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I896

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y?;<

CONTENTS.

GENERAL.

PAGE

African Grass Fires and their Effects. By G. F. Scott Elliott, M.A. 77

The Past, Present, and Future Water Supply of London. By E.

Frankland, F.R.S. 163

Gold Extraction Processes. By T. K. Rose, D.Sc, Assistant Assayer

of the Royal Mint ------- 484

ANIMAL MORPHOLOGY.

The Morphology of the Mollusca. By. W. Garstang, M.A., Fellow

of Lincoln College, Oxford 38

The Present Position of the Cell Theory, By G. C. Bourne, M.A.,

Fellow of New College, Oxford - - -94,227,304

Some Recent Memoirs upon Oligochfeta. By F. E. Beddard,

M.A., F.R.S. 19°

ANTHROPOLOGY.

Pre-historic Man in the Eastern Mediterranean. By J. L. Myers,

Fellow of Magdalen College, Oxford - - 335

Selection in Man. By John Beddoe, M.D., LL.D., F.R.S. - - 384

BOTANY.

On Recent Advances in Vegetable Cytology. By J. Bretland Farmer,
M.A., Professor of Botany in the Royal College of Science,
London - ---------22

The Reserve Materials of Plants [Concluded). By J. Reynolds
Green, M.A., F.R.S., Professor of Botany to the Pharma-
ceutical Society, London ------ 60

The Stelar Theory : A History and a Criticism. By A. G. Tansley,

B.A. i33j 215

Ferns : Aposporous and Apogamous. By C. T. Druery, F.L.S. - 242

Insular Floras. By W. Botting Hemsley, F.R.S.- - - 286,374

CHEMISTRY AND PHYSICS.

The General Bearings of Magnetic Observations. By Captain Ettrick
W. Creak, R.N., F.R.S., Superintendent of Compasses to
the Admiralty - - - - - - - - - 81

Solid Solutions. By James Walker, Ph.D., D.Sc, Professor of

Chemistry in University College, Dundee - - - - 121

2 /Sf&

vi CONTENTS.

PAGE

Notes on Atomic Weights. By Alexander Scott, M.A., Jacksonian

Demonstrator in the University of Cambridge - 202

The Growth of our Knowledge of Helium. By J. Norman Lockyer,

C.B., F.R.S. --------- 249

Light and Electrification. By Oliver Lodge, F.R.S., Professor of

Physics in University College, Liverpool - - - - 417

Recent Values of the Magnetic Elements at the Principal Magnetic
Observatories of the World. By Charles Chree, M.A.,
Superintendent of Kew Observatory - - - - - 499

T

GEOLOGY, MINERALOGY AND PALAEONTOLOGY

The Graptolites. By J. E. Marr, M.A., F.R.S., Fellow of St. John's

College, Cambridge -------- 360

Recent Discoveries in Avian Palaeontology. By C. W. Andrews - 398
An Extinct Plant of Doubtful Affinity. By A. C. Seward, M.A.,

F.G.S., University Lecturer in Botany, Cambridge - 428

The Work of the Portuguese Geological Survey. By Philip Lake,

M. A., St. John's College, Cambridge- - 439

Petrology in America. By Alfred Harker, M. A., Fellow of St. John's

College, Cambridge- ------- 459

PATHOLOGY.

The Hereditary Transmission of Micro-organisms. By G. A. Buck-
master, M.D., Lecturer on Physiology at St. George's Hospital,

London ---------- 324

PHYSIOLOGY.

Ludwig and Modern Physiology. By J. Burdon Sanderson, M.D.,
F.R.S., Regius Professor of Physiology in the University of
Oxford ---------- 1

On Some Applications of the Theory of Osmotic Pressures to
Physiological Problems (Part II.). By E. H. Starling, M.D.,
Lecturer on Physiology at Guy's Hospital, London - - 151

Iodine in the Animal Organism. By W. D. Halliburton, M.D.,

F.R.S., Professor of Physiology in King's College, London - 454

APPENDIX I.
Notices of Books, - - - - - - 1, xi, xxi, xxxi, xli

APPENDIX II.
Titles of Chemical Papers, - iv, xv, xxv, xxxm, xlii, xlvii

ALPHABETICAL LIST OF AUTHORS.

PAGE

Andrews, C W. Recent Discoveries in Avian Palaeontology - 398

Beddard, F. E. Some Recent Memoirs upon Oligochaeta - 190

Beddoe, John. Selection in Man - 384

Bourne, G. C. The Present Position of the Cell Theory 94, 227, 304
Buckmaster, G. A. The Hereditary Transmission of Micro-
organisms - - - - - - - ~324

Chree, Charles. Recent Values of the Magnetic Elements - - 499
Creak, Captain Ettrick. The General Bearings of Magnetic Observa-
tions ___-__--- 81
Druery, C. T. Ferns : Aposporous and Apogamous - - 242
Farmer, J. B. On Recent Advances in Vegetable Cytology - - 22
Frankland, E. The Past, Present and Future Water Supply of

London ------- 163

Garstang, W. The Morphology of the Mollusca - 38

Green, J. Reynolds. The Reserve Materials of Plants - 60

Halliburton, W. D. Iodine in the Animal Organism - 454

Harker, Alfred. Petrology in America - - 459
Hemsley, W. Botting. Insular Floras - - - 286, 374

Lake, Philip. The Work of the Portuguese Geological Survey 439

Lockyer, J. Norman. The Growth of our Knowledge of Helium - 249

Lodge, Oliver. Light and Electrification - - - - - 417

Marr, J. E. The Graptolites ------ 360

Myers, J. L. Prehistoric Man in the Eastern Mediterranean - 335

Rose, T. R. Gold Extraction Processes ----- 484

Sanderson, J. Burdon. Ludwig and Modern Physiology - - 1

Scott, Alexander. Notes on Atomic Weights ... - 202

Scott-Elliott, G. F. African Grass Fires and their Effects - - 77

Seward, A. C. An Extinct Plant of Doubtful Affinity - 428
Starling, E. H. On some Applications of the Theory of Osmotic

Pressures to Physiological Problems - - - - - 151

Tansley, A. G. The Stellar Theory - 133,215

Walker, James. Solid Solutions - - - - - - - 121

l-\\

Btimce progress

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No. 25.

March, 1896.

Vol. V.

LUDWIG AND MODERN PHYSIOLOGY.1

I. INTRODUCTION.

THE death of any discoverer — of any one who has
added largely to the sum of human knowledge —
affords a reason for inquiring what his work was and how
he accomplished it. This inquiry has interest even when
the work has been completed in a few years and has been
limited to a single line of investigation — much more when
the life has been associated with the origin and develop-
ment of a new science and has extended over half a
century.

The Science of Physiology as we know it came into
existence fifty years ago with the beginning of the active life
of Ludwig, in the same sense that the other great branch of
Biology, the Science of Living Beings (Ontology), as we
now know it, came into existence with the appearance of the
" Origin of Species ". In the order of time Physiology had
the advantage, for the new Physiology was accepted some
ten years before the Darwinian epoch. Notwithstanding, the
content of the science is relatively so unfamiliar, that before
entering: on the discussion of the life and work of the man
who, as I shall endeavour to show, had a larger share in
founding it than any of his contemporaries, it is necessary
to define its limits and its relations to other branches of
knowledge.

1 Founded upon a lecture delivered at the Royal Institution, Jan.
24, 1896.

2 SCIENCE PROGRESS.

The word Physiology has in modern times changed its
meaning. It once comprehended the whole knowledge of
Nature. Now it is the name for one of the two Divisions
of the Science of Life. In the progress of investigation
the study of that Science has inevitably divided itself into
two : Ontology, the Science of Living Beings ; Physiology,
the Science of Living Processes, and thus, inasmuch as
Life consist in processes, of Life itself. Both strive to
understand the complicated relations and endless varieties
which present themselves in living Nature, but by different
methods. Both refer to general principles, but they are of
a different nature.

To the Ontologist, the student of Living Beings, Plants
or Animals, the great fact of Evolution, namely, that from
the simplest beginning our own organism, no less than that
of every animal and plant with its infinite complication of
parts and powers, unfolds the plan of its existence — taken
with the observation that that small beginning was, in all
excepting the lowest forms, itself derived from two parents,
equally from each — is the basis from which his study and
knowledge of the world of living beings takes its departure.
For on these two facts — Evolution and Descent — the ex-
plorer of the forms, distribution and habits of animals and
plants has, since the Darwinian epoch, relied with an ever-
increasing certainty, and has found in them the explanation
of every phenomenon, the solution of every problem relating
to the subject of his inquiry. Nor could he wish for a more
secure basis. Whatever doubts or misgivings exist in the
minds of " non-biologists " in relation to it, may be attributed
partly to the association with the doctrine of Evolution of
questions which the true naturalist regards as transcen-
dental ; partly to the perversion or weakening of meaning
which the term has suffered in consequence of its introduc-
tion into the language of common life, and particularly to
the habit of applying it to any kind of progress or improve-
ment, anything which from small beginnings gradually
increases. But, provided that we limit the term to its
original sense — the Evolution of a living being from its
germ by a continuous, not a gradual process — there is no

LUDWIG AND MODERN PHYSIOLOGY. 3

conception which is more free from doubt either as to its
meaning or reality. It is inseparable from that of Life
itself, which is but the unfolding of a predestined harmony,
of a prearranged consensus and synergy of parts.

The other branch of Biology, that with which Ludwig's
name is associated, deals with the same facts in a different
way. While Ontology regards animals and plants as in-
dividuals and in relation to other individuals, Physiology
considers the processes themselves of which life is a complex.
This is the most obvious distinction, but it is subordinate to
the fundamental one, namely, that while Ontology has for
its basis laws which are in force only in its own province,
those of Evolution, Descent, and Adaptation, we Physiolo-
gists, while accepting these as true, found nothing upon them,
using them only for euristic purposes, i.e., as guides to dis-
covery, not for the purpose of explanation. Purposive Adapta-
tion, for example, serves as a clue, by which we are constantly
guided in our exploration of the tangled labyrinth of vital
processes. But when it becomes our business to explain
these processes — to say how they are brought about — we
refer them not to biological principles of any kind, but to
the Universal Laws of Nature. Hence it happens that
with reference to each of these processes, our inquiry is
rather how it occurs than why it occurs.

It has been well said that the Natural Sciences are the
children of necessity. Just as the other Natural Sciences
owed their origin to the necessity of acquiring that control
over the forces of Nature without which life would
scarcely be worth living, so Physiology arose out of human
suffering and the necessity of relieving it. It sprang indeed
out of Pathology. It was suffering that led us to know, as
regards our own bodies, that we had internal as well as
external organs, and probably one of the first generalisa-
tions which arose out of this knowledge was, that " if one
member suffer all the members suffer with it " — that all
work together for the good of the whole. In earlier times
the good which was thus indicated was associated in men's
minds with human welfare exclusively. But it was
eventually seen that Nature has no less consideration for

4 SCIENCE PROGRESS.

the welfare of those of her products which to us seem
hideous or mischievous, than for those which we regard
as most useful to man or most deserving of his admiration.
It thus became apparent that the good in question could not
be human exclusively, but as regards each animal its oivn
good — and that in the organised world the existence and
life of every species is brought into subordination to one
purpose — its own success in the struggle for existence.1

From what has preceded it may be readily understood
that in Physiology, Adaptation takes a more prominent
place than Evolution or Descent. In the prescientific
period adaptation was everything. The observation that
any structure or arrangement exhibited marks of adaptation
to a useful purpose was accepted not merely as a guide in
research, but as a full and final explanation. Of an organism
or organ which perfectly fulfilled, in its structure and work-
ing, the end of its existence, nothing further required to be
said or known. Physiologists of the present day recognise
as fully as their predecessors that perfection of contrivance
which displays itself in all living structures, the more ex-
quisitely the more minutely they are examined. No one,
for example, has written more emphatically on this point
than did Ludwig. In one of his discourses, after showing
how Nature exceeds the highest standard of human attain-
ment — how she fashions as it were out of nothing and with-
out tools, instruments of a perfection which the human
artificer cannot reach, though provided with every suitable
material — wood, brass, glass, india-rubber — he gives the
organ of sight as a signal example, referring among its

1 1 am aware that in thus stating the relation between adaptation and the
struggle for existence, I may seem to be reversing the order followed by
Mr. Darwin, inasmuch as he regarded the survival of organisms which are
fittest for their place in Nature, and of parts which are fittest for their
place in the organism, as the agency by which adaptedness is brought about.
However this may be expressed it cannot be doubted that fitness is an
essential of organisms. Living beings are the only things in Nature which
by virtue of evolution and descent are able to adapt themselves to their
surroundings. It is therefore only so far as organism (with all its attri-
butes) is presupposed, that the dependence of adaptation on survival is
intelligible.

LUDWIG AND MODERN PHYSIOLOGY. 5

other perfections to the rapidity with which the eye can
be fixed on numerous objects in succession and the instan-
taneous and unconscious estimates which we are able to
form of the distances of objects, each estimate involving a
process of arithmetic which no calculating machine could
effect in the time.1 In another discourse — that given at
Leipzig when he entered on his professorship in 1865 — he re-
marks that when in our researches into the finer mechanism
of an organ we at last come to understand it, we are
humbled by the recognition " that the human inventor is
but a blunderer as compared with the unknown Master of
the animal creation ",2

Some readers will perhaps remember how one of the
most brilliant of philosophical writers, in a discourse to the
British Association delivered a quarter of a century ago,
averred on the authority of a great Physiologist that the
eye, regarded as an optical instrument, was so inferior a
production that if it were the work of a mechanician it
would be unsaleable. Without criticising or endeavouring
to explain this paradox, I may refer to it as having given
the countenance of a distinguished name to a misconception
which I know exists in the minds of many persons, to the
effect that the scientific Physiologist is more or less blind to
the evidence of design in creation. On the contrary, the
view taken by Ludwig, as expressed in the words I have
quoted, is that of all Physiologists. The disuse of the
teleological expressions which were formerly current does
not imply that the indications of contrivance are less ap-
preciated, for, on the contrary, we regard them as more
characteristic of organism as it presents itself to our obser-
vation than any other of its endowments. But, if I may

1 I summarise here from a very interesting lecture entitled " Leid und
Freude in der Naturforschung " published in the Gartenlaube (Nos. 22 and
23) in 1870.

2 The words translated in the above sentence are as follows : " Wenn
uns endlich die Palme gereicht wird, wenn wir ein Organ in seinem
Zuzammenhang begreifen, so wird unser stolzes Gattungsbewusstsein durch
die Erkenntniss niedergedruckt, dass der menschlicher Erfinder ein Stumper
gegen den unbekannten Meister der thierischen Schbpfung sei ".

6 SCIENCE PROGRESS.

be permitted to repeat what has been already said, we use
the evidences of adaptation differently. We found no ex-
planation on this or any other biological principle, but refer
all the phenomena by which these manifest themselves to
the simpler and more certain Physical Laws of the Universe.

Why must we take this position ? First, because it is a
general rule in investigations of all kinds to explain the
more complex by the more simple. The material Universe
is manifestly divided into two parts, the living and the non-
living. We may, if we like, take the living as our Norma,
and say to the Physicists, You must come to us for Laws,
you must account for the play of energies in universal nature
by referring them to Evolution, Descent, Adaptation. Or
we may take these words as true expressions of the mutual
relations between the phenomena and processes peculiar to
living beings, using for the explanation of the processes
themselves the same methods which we should employ if
we were engaged in the investigation of analogous pro-
cesses going on independently of life. Between these two
courses there seems to me to be no third alternative, unless
we suppose that there are two material Universes, one to
which the material of our bodies belongs, the other com-
prising everything that is not either plant or animal.

The second reason is a practical one. We should have
to go back to the time which I have ventured to call pre-
scientific, when the world of life and organisation was sup-
posed to be governed exclusively by its own Laws. The
work of the past fifty years has been done on the opposite
principle, and has brought light and clearness where there
was before obscurity and confusion. All this progress we
should have to repudiate, but this would not be all. We
should have to forego the prospect of future advance.
Whereas by holding on our present course, gradually pro-
ceeding from the more simple to the more complex, from
the physical to the vital, we may confidently look forward
to extending our knowledge considerably beyond its present
limits.

A no less brilliant writer than the one already referred
to, who is also no longer with us, asserted that mind was a

LUDWIG AND MODERN PHYSIOLOGY. y

secretion of the brain in the same sense that bile is a secretion
of the liver or urine that of the kidney ; and many people
have imagined this to be the necessary outcome of a too
mechanical way of looking at vital phenomena, and that
Physiologists, by a habit of adhering strictly to their own
method, have failed to see that the organism presents prob-
lems to which this method is not applicable, such, e.g., as
the origin of the organism itself, or the origin and develop-
ment in it of the mental faculty. The answer to this sug-
gestion is that these questions are approached by Physio-
logists only in so far as they are approachable. We are
well aware that our business is with the unknown knowable,
not with the transcendental. During the last twenty years
there has been a considerable forward movement in Physio-
logy in the psychological direction, partly dependent on
discoveries as to the localisation of the higher functions of
the nervous system, partly on the application of methods of
measurement to the concomitant phenomena of psychical
processes. And these researches have brought us to the
very edge of a region which cannot be explored by our
methods — where measurements of time or of space are no
longer possible.

In approaching this limit the Physiologist is liable to fall
into two mistakes — on the one hand, that of passing into
the transcendental without knowing it ; on the other, that
of assuming that what he does not know is not knowledge.
The first of these risks seems to me of little moment ; first,
because the limits of natural knowledge in the psychological
direction have been well defined by the best writers, as, e.g.,
by du Bois-Reymond in his well-known essay "On the
Limits of Natural Knowledge," but chiefly because the in-
vestigator who knows what he is about is arrested in limine
by the impossibility of applying the experimental method
to questions beyond its scope. The other mistake is chiefly
fallen into by careless thinkers, who, while they object to
the employment of intuition even in regions where intuition
is the only method by which anything can be learned,
attempt to describe and define mental processes in mechan-
ical terms, assigning to these terms meanings which science

8 SCIENCE PROGRESS.

does not recognise, and thus slide into a kind of speculation
which is as futile as it is unphilosophical.

II. LUDWIG AS INVESTIGATOR AND TEACHER.

The uneventful history of Ludwig's life — how early he
began his investigation of the anatomy and function of the
kidneys ; how he became just fifty years ago titular Pro-
fessor at Marburg, in the small University of his native
State, Hesse Cassel ; how in 1849 he removed to Zurich as
actual Professor and thereupon married ; how he was six
years later promoted to Vienna — has already been admirably
related in these pages by Dr. Stirling. In 1865, after
twenty years of professorial experience, but still in the
prime of life and, as it turned out, with thirty years of
activity still before him, he accepted the Chair of Physio-
logy at Leipzig. His invitation to that great University
was by far the most important occurrence in his life, for the
liberality of the Saxon Government, and particularly the
energetic support which he received from the enlightened
Minister v. Falkenstein, enabled him to accomplish for
Physiology what had never before been attempted on an
adequate scale. No sooner had he been appointed than
he set himself to create what was essential to the
progress of the Science — a great Observatory, arranged
not as a Museum, but much more like a physical and
chemical Laboratory, provided with all that was needed for
the application of exact methods of research to the investiga-
tion of the processes of Life. The idea which he had ever in
view, and which he carried into effect during the last thirty
years of his life with signal success, was to unite his life-
work as an investigator with the highest kind of teaching.
Even at Marburg and at Zurich he had begun to form a
School ; for already men nearly of his own age had rallied
round him. Attracted in the first instance by his early
discoveries, they were held by the force of his character,
and became permanently associated with him in his work
as his loyal friends and followers — in the highest sense his
scholars. If, therefore, we speak of Ludwig as one of the

LUDWIG AND MODERN PHYSIOLOGY. o,

greatest teachers of Science the world has seen, we
have in mind his relation to the men who ranged them-
selves under his leadership in the building up of the Science
of Physiology, without reference to his function as an
ordinary academical teacher.

Of this relation we can best judge by the careful perusal
of the numerous biographical memoirs which have appeared
since his death, more particularly those of Professor His1
(Leipzig), of Professor Kronecker2 (Bern), who was for
many years his coadjutor in the Institute, of Professor v.
Fick 3 (Wlirzburg), of Professor v. Kries * (Freiburg), of
Professor Mosso5 (Turin), of Professor Fano 6 (Florence),
of Professor Tigerstedt 7 (Upsala), of Professor Stirling s
in England. With the exception of Fick, whose relations with
Ludwig were of an earlier date, and of his colleague in the
Chair of Anatomy, all of these distinguished teachers were
at one time workers in the Leipzig Institute. All testify
their love and veneration for the master, and each contributes
some striking touches to the picture of his character.

All Ludwig's investigations were carried out with his
scholars. He possessed a wonderful faculty of setting each
man to work at a problem suited to his talent and previous
training, and this he carried into effect by associating him
with himself in some research which he had either in
progress or in view. During the early years of the Leip-
zig period, all the work done under his direction was
published in the well-known volumes of the Arbeiten, and

1 His. " Karl Ludwig und Karl Thiersch.'' Akademische Geddcht-
nissrede, Leipzig, 1S95.

2 Kronecker. "Carl Friedrich Wilhelm Ludwig." Berliner Klin,
Wochensch., 1895, No. 21.

3 A. Fick. " Karl Ludwig." Nachruf. Biographische Blatter, Berlin,
vol. i., pt. 3.

4 v. Kries. "Carl Ludwig." Freiburg, Bd. i., 1895.

5 Mosso. " Karl Ludwig." Die Nation, Berlin, Nos. 38, 39.

6 Fano. " Per Carlo Ludwig Commemorazione." Clinica Afodema,
Florence, i., No. 7.

7 Tigerstedt. " Karl Ludwig." Denkrede. Biographische Blatter, Berlin,
vol. i., pt. 3.

8 Stirling. "Science Progress," vol. iv., No. 21.

io SCIENCE PROGRESS.

subsequently in the Archiv fur Anat. unci Physiologic of
du Bois-Reymoncl. Each " Arbeit ': of the laboratory
appeared in print under the name of the scholar who
operated with his master in its production, but the
scholar's part in the work done varied according to its
nature and his ability. Sometimes, as v. Kries says, he sat
on the window-sill while Ludwig with the efficient help of
his laboratory assistant Salvenmoser, did the whole of the
work. In all cases Ludwig not only formulated the
problem, but indicated the course to be followed in each
step of the investigation, calling the worker, of course, into
counsel. In the final working up of the results he always
took a principal part, and often wrote the whole paper. But
whether he did little or much, he handed over the whole
credit of the performance to his coadjutor. This method of
publication has no doubt the disadvantage that it leaves
it uncertain what part each had taken ; but it is to be
remembered that this drawback is unavoidable whenever
master and scholar work together, and is outweighed by the
many advantages which arise from this mode of co-opera-
tion. The instances in which any uncertainty can exist in
relation to the real authorship of the Leipzig work are
exceptional. The well-informed reader does not need to
be told that Mosso or Schmidt, Brunton or Gaskell, Stirling
or Wooldridge were the authors of their papers in a sense
very different from that in which the term could be applied
to some others of Ludwig's pupils. On the whole the plan
must be judged of by the results. It was by working with
his scholars that Ludwig trained them to work afterwards by
themselves ; and thereby accomplished so much more than
other great teachers have done.

I do not think that any of Ludwig's contemporaries
could be compared to him in respect of the wide range of
his researches. In a science distinguished from others by
the variety of its aims, he was equally at home in all
branches, and was equally master of all methods, for he
recognised that the most profound biological question can
only be solved by combining anatomical, physical and
and chemical inquiries. It was this consideration which led

LUDWIG AND MODERN PHYSIOLOGY. n

him in planning the Leipzig Institute to divide it into three
parts, experimental (in the more restricted sense), chemical
and histological. Well aware that it was impossible for a
man who is otherwise occupied to maintain his familiarity
with the technical details of Histology and Physiological
Chemistry, he placed these departments under the charge
of younger men capable of keeping them up to the rapidly
advancing standard of the time, his relations with his
coadjutors being such that he had no difficulty in retaining
his hold of the threads of the investigation to which these
special lines of inquiry were contributory.

It is scarcely necessary to say that as an experimenter
Ludwig was unapproachable. The skill with which he
carried out difficult and complicated operations, the care
with which he worked, his quickness of eye and certainty
of hand were qualities which he had in common with great
surgeons. In employing animals for experiment he strongly
objected to rough and ready methods, comparing them to
" firing a pistol into a clock to see how it works ". Every
experiment ought, he said, to be carefully planned and
meditated on beforehand, so as to accomplish its scientific
purpose and avoid the infliction of pain. To ensure this
he performed all operations himself, only rarely committing
the work to a skilled coadjutor.

His skill in anatomical work was equally remarkable.
It had been acquired in early days, and appeared throughout
his life to have given him very great pleasure, for Mosso
tells how, when occupying the room adjoining that in which
Ludwig was working as he usually did by himself, he heard
the outbursts of glee which accompanied each successful step
in some difficult anatomical investigation.

Let us now examine more fully the part which Ludwig
played in the revolution of ideas as to the nature of vital
processes which, as we have seen, took place in the middle
of the present century.

Although, as we shall see afterwards, there were many
men who, before Ludwig's time, investigated the phenomena
of life from the physical side, it was he and the contem-
poraries who were associated with him who first clearly

12 SCIENCE PROGRESS.

recognised the importance of the principle that vital pheno-
mena can only be understood by comparison with their physical
counterparts, and foresaw that in this principle the future of
Physiology was contained as in a nutshell. Feeling strongly
the fruitlessness and unscientific character of the doctrines
which were then current, they were eager to discover
chemical and physical relations in the processes of life.
In Ludwig's intellectual character this eagerness expressed
his dominant motive. Notwithstanding that his own re-
searches had in many instances proved that there are im-
portant functions and processes in the animal organism
which have no physical or chemical analogues, he never
swerved either from the principle or from the method
founded upon it.

Although Ludwig was strongly influenced by the rapid
progress which was being made in scientific discovery at
the time that he entered on his career, he derived little from
his immediate predecessors in his own science. He is
sometimes placed among the pupils of the great Comparative
Anatomist and Physiologist, J. Mliller. This, however, is a
manifest mistake, for Ludwig did not visit Berlin until 1847,
when Miiller was nearly at the end of his career. At that
time he had already published researches of the highest
value (those on the Mechanism of the Circulation and on the
Physiology of the Kidney), and had set forth the line in
which he intended to direct his investigations. The only
earlier Physiologist with whose work that of Ludwig can
be said to be in real continuity was E. H. Weber, whom he
succeeded at Leipzig, and strikingly resembled in his way
of working. For Weber, Ludwig expressed his veneration
more unreservedly than for any other man, excepting per-
haps Helmholtz, regarding his researches as the foundation
on which he himself desired to build. Of his colleagues at
Marburg he was indebted in the first place to the anatomist,
Professor Ludwig Fick, in whose department he began his
career as Prosector, and to whom he owed facilities without
which he could not have carried out his earlier researches ;
and in an even higher degree to the great chemist, R. W.
Bunsen, from whom he derived that training in the exact

LUDWIG AND MODERN PHYSIOLOGY. 13

sciences which was to be of such inestimable value to him
afterwards.

There is reason, however, to believe that, as so often
happens, Ludwig's scientific progress was much more in-
fluenced by his contemporaries than by his seniors. In
1847, as we learn on the one hand from du Bois-Reymond,
on the other from Ludwig himself, he visited Berlin for the
first time. This visit was an important one both for him-
self and for the future of Science, for he there met three
men of his own age, Helmholtz, du Bois-Reymond and
Brticke, who were destined to become his life-friends, all of
whom lived nearly as long as Ludwig himself, and attained
to the highest distinction. They all were full of the same
enthusiasm. As Ludwig said when speaking of this visit :
" We four imagined that we should constitute Physiology
on a chemico-physical foundation, and give it equal scientific
rank with Physics, but the task turned out to be much more
difficult than we anticipated ". These three young men,
who were devoted disciples of the great Anatomist, had the
advantage over their master in the better insight which
their training had given them into the fundamental prin-
ciples of scientific research. They had already gathered
around themselves a so-called "physical " school of Physio-
logy, and welcomed Ludwig on his arrival from Marburg
as one who had of his own initiative undertaken in his own
University das Befremngswerk aus dcm Vitalismus.

The determination to refer all vital phenomena to their
physical or chemical counterparts or analogues, which, as I
have said, was the dominant motive in Ludwio's char-
acter, was combined with another quality of mind which if
not equally influential was even more obviously displayed in
his mode of thinking and working. His first aim, even
before he sought for any explanation of a structure or of
a process, was to possess himself, by all means of observa-
tion at his disposal, of a complete objective conception of
all its relations. He regarded the faculty of vivid sensual
realisation (lebendige sinnliche Anschanung) as of special
value to the investigator of natural phenomena, and did his
best to cultivate it in those who worked with him in the

14 SCIENCE PROGRESS.

laboratory. In himself, this objective tendency (if I may
be permitted the use of a word which, if not correct, seems
to express what I mean) might be regarded as almost a
defect, for it made him indisposed to appreciate any sort of
knowledge which deals with the abstract. He had a
disinclination to philosophical speculation which almost
amounted to aversion, and, perhaps for a similar reason,
avoided the use of mathematical methods even in the
discussion of scientific questions which admitted of being
treated mathematically — contrasting in this respect with
his friend du Bois-Reymond, resembling Brlicke. But
as a teacher the quality was of immense use to him. His
power of vivid realisation was the substratum of that many-
sidedness which made him, irrespectively of his scientific
attainments, so attractive a personality.

I am not sure that it can be generally stated that a keen
scientific observer is able to appreciate the artistic aspects
of Nature. In Ludwig's case, however, there is reason to
think that aesthetic faculty was as developed as the power of
scientific insight. He was a skilful draughtsman but not
a musician ; both arts were, however, a source of enjoy-
ment to him. He was a regular frequenter of the Gewand-
kaus concerts, and it was his greatest pleasure to bring to-
gether gifted musicians in his house, where he played the
part of an intelligent and appreciative listener. Of painting
he knew more than of music, and was a connoisseur whose
opinion carried weight. It is related that he was so worried
by what he considered bad art, that after the redecoration
of the Gczvandhaus concert-room, he was for some time
deprived of his accustomed pleasure in listening to music.

Ludwig's social characteristics can only be touched on
here in so far as they serve to make intelligible his wonder-
ful influence as a teacher. Many of his pupils at Leipzig
have referred to the schbne Gemeinsamkeit which char-
acterised the life there. The harmonious relation which,
as a rule, subsisted between men of different education and
different nationalities, could not have been maintained had
not Ludwig possessed side by side with that inflexible
earnestness which he showed in all matters of work or

LUDWIG AND MODERN PHYSIOLOGY. 15

duty a certain youthfulness of disposition which made it
possible for men much younger than himself to accept his
friendship. This sympathetic geniality was, however, not
the only or even the chief reason why Ludwig's pupils were
the better for having known him. There were not a few
of them who for the first time in their lives came into
personal relation with a man who was utterly free from
selfish aims and vain ambitions, who was scrupulously
conscientious in all that he said and did, who was what he
seemed, and seemed what he was, and who had no other
aim than the advancement of his science, and in that ad-
vancement saw no other end than the increase of human
happiness. These qualities displayed themselves in Lud-
wig's daily active life in the laboratory, where he was to be
found whenever work of special interest was going on ; but
still more when, as happened on Sunday mornings, he was
"at home" in the library of the Institute — the corner room
in which he ordinarily worked. Many of his "scholars"
have put on record their recollections of these occasions, the
cordiality of the master's welcome, the wide range and
varied interest of his conversation, and the ready apprecia-
tion with which he seized on anything that was new or
original in the suggestions of those present. Few men
live as he did, " im Gaznen, Gtiten, Sckonen" and of those
still fewer know how to communicate out of their fulness to
others.

III. THE OLD AND THE NEW VITALISM.

Since the middle of the century the progress of Physio-
logy has been continuous. Each year has had its record,
and has brought with it new accessions to knowledge. In
one respect the rate of progress was more rapid at first than
it is now, for in an unexplored country discovery is relatively
easy. In another sense it was slower, for there are now
scores of investigators for every one that could be counted
in 1840 or 1850. Until recently there has been throughout
this period no tendency to revert to the old methods — no
new departure — no divergence from the principles which
Ludwig did so much to enforce and exemplify.

16 SCIENCE PROGRESS.

The wonderful revolution which the appearance of the
Origin of Species produced in the other branch of Biology,
promoted the progress of Physiology, by the new interest
which it gave to the study, not only of structure and de-
velopment, but of all other vital phenomena. It did not,
however, in any sensible degree affect our method or alter
the direction in which Physiologists had been working for
two decades. Its most obvious effect was to sever the two
subjects from each other. To the Darwinian epoch Com-
parative Anatomy and Physiology were united, but as the
new Ontology grew, it became evident that each had its own
problems and its own methods of dealing with them.

The old vitalism of the first half of the century is easily
explained. It was generally believed that, on the whole,
things went on in the living body as they do outside of
it, but when a difficulty arose in so explaining them the
Physiologist was ready at once to call in the aid of a
" vital force' '. It must not, however, be forgotten that, as I
have already indicated, there were great teachers (such,
for example, as Sharpey and Allen Thomson in England,
Magendie in France, Weber in Germany) who discarded
all vitalistic theories, and concerned themselves only with
the study of the time- and place-relations of phenomena ;
men who were before their time in insight, and were only
hindered in their application of chemical and physical prin-
ciples to the interpretation of the processes of life by the
circumstance that chemical and physical knowledge was in
itself too little advanced. Comparison was impossible, for
the standards were not forthcoming.

Vitalism in its original form gave way to the rapid ad-
vance of knowledge as to the correlation of the physical
sciences which took place in the forties. Of the. many
writers and thinkers who contributed to that result, J. R.
Mayer and Helmholtz did so most directly, for the con-
tribution of the former to the establishment of the Doctrine
of the Conservation of Energy had physiological considera-
tions for its point of departure ; and Helmholtz, at the time
he wrote the Erhaltung der Kraft, was still a Physiolo-
gist. Consequently when Ludwig's celebrated Lehrbuch

LUDWIG AND MODERN PHYSIOLOGY. 17

came out in 1852, the book which gave the coup de grace to
vitalism in the old sense of the word, his method of setting
forth the relations of vital phenomena by comparison with
their physical or chemical counterparts, and his assertion that
it was the task of Physiology to make out their necessary
dependence on elementary conditions, although in violent
contrast with current doctrine, were in no way surprising to
those who were acquainted with the then recent progress
of research. Ludwig's teaching was indeed no more than
a general application of principles which had already been
applied in particular instances.

The proof of the non-existence of a special " vital force "
lies in the demonstration of the adequacy of the known
sources of energy in the organism to account for the actual
day by day expenditure of heat and work — in other words,
on the possibility of setting forth an energy balance sheet in
which the quantity of food which enters the body in a given
period (hour or day) is balanced by an exactly correspond-
ing amount of heat produced or external work done. It is
interesting to remember that the work necessary for
preparing such a balance sheet (which Mayer had attempted,
but, from want of sufficient data, failed in) was begun
thirty years ago in the laboratory of the Royal Institution
by the Foreign Secretary of the Royal Society. But the
determinations made by Dr. Frankland related to one side of
the balance sheet, that of income. By his researches in 1 866
he gave Physiologists for the first time reliable information
as to the heat value {i.e., the amount of heat yielded by the
combustion) of different constituents of food. It still re-
mained to apply methods of exact measurement to the
expenditure side of the account. Helmholtz had estimated
this, as regards man, as best he might, but the technical
difficulties of measuring the expenditure of heat of the
animal body appeared until lately to be almost insuperable.
Now that it has been at last successfully accomplished, we
have the experimental proof that in the process of life there
is no production or disappearance of energy. It may be
said that it was unnecessary to prove what no scientifically

sane man doubted. There are, however, reasons why it is

2

18 SCIENCE PROGRESS.

of importance to have objective evidence that food is the
sole and adequate source of the energy which we day by
day or hour by hour disengage, whether in the form of heat
or external work.

In the opening paragraph of this section it was observed
that until recently there had been no tendency to revive the
vitalistic notion of two generations ago. In introducing the
words in italics I referred to the existence at the present
time in Germany of a sort of reaction, which under the
term " Neovitalismus " has attracted some attention — -so
much indeed that at the Versani7nlung Deutscher Natur-
forscher at Ltibeck last September, it was the subject of
one of the general addresses. The author of this address,
Prof. Rindfleisch, was, I believe, the inventor of the word ;
but the origin of the movement is usually traced to a work
on Physiological Chemistry which an excellent translation
by the late Dr. Wooldridge has made familiar to English
students. The author of this work owes it to the language
he employs in the introduction on " Mechanism and
Vitalism," if his position has been misunderstood, for in
that introduction he distinctly ranges himself on the vital-
istic side. As, however, his vitalism is of such a kind as
not to influence his method of dealing with actual problems,
it is only in so far of consequence as it may affect the reader.
For my own part I feel grateful to Professor Bange for
having produced an interesting and readable book on a dry
subject, even though that interest may be partly due to the
introduction into the discussion of a question which, as he
presents it, is more speculative than scientific.

As regards other physiological writers to whom vitalistic
tendencies have been attributed, it is to be observed that
none of them have even suggested that the doctrine of a
"vital force" in its old sense should be revived. Their
contention amounts to little more than this, that in certain
recent instances improved methods of research appear to
have shown that processes at first regarded as entirely
physical or chemical do not conform so precisely as they
were expected to do to chemical and physical laws. As
these instances are all essentially analogous, reference to
one will serve to explain the bearing of the rest.

LUDWIG AND MODERN PHYSIOLOGY. 19

Those who have any acquaintance with the structure of
the animal body will know that there exists in the higher
animals, in addition to the system of veins by which the
blood is brought back from all parts to the heart, another
less considerable system of branched tubes, the lymphatics,
by which, if one may so express it, the leakage of the blood-
vessels is collected. Now, without inquiring into the why
of this system, Ludwig and his pupils made and continued
for many years elaborate investigations which were for long
the chief sources of our knowledge, their general result
being that the efficient cause of the movement of the lymph,
like that of the blood, was mechanical. At the Berlin Con-
gress in 1890 new observations by Professor Heidenhain of
Breslau made it appear that under certain conditions the
process of lymph formation does not go on in strict accord-
ance with the physical laws by which leakage through
membranes is regulated, the experimental results being of
so unequivocal a kind that, even had they not been con-
firmed, they must have been received without hesitation.
How is such a case as this to be met? The "Neovitalists "
answer promptly by reminding us that there are cells, i.e.,
living individuals, placed at the inlets of the system of
drainage without which it would not work, that these let in
less or more liquid according to circumstances, and that in
doing so they act in obedience, not to physical laws, but to
vital ones — to internal laws which are special to themselves.

Now, it is perfectly true that living cells, like working
bees, are both the architects of the hive and the sources of
its activity, but if we ask how honey is made it is no answer
to say that the bees make it. We do not require to be told
that cells have to do with the making of lymph as with
every process in the animal organism, but what we want to
know is how they work, and to this we shall never get an
answer so long as we content ourselves with merely ex-
plaining one unknown thing by another. The action of
cells must be explained, if at all, by the same method of
comparison with physical or chemical analogues that we
employ in the investigation of organs.

Since 1890 the problem of lymph formation has been

20 SCIENCE PROGRESS.

attacked by a number of able workers, among others here
in London, by Dr. Starling of Guy's Hospital, who, by
sedulously studying the conditions under which the dis-
crepancies between the actual and the expected have arisen,
has succeeded in untying several knots. In reference to
the whole subject, it is to be noticed that the process by
which difficulties are brought into view is the same as that
by which they are eliminated. It is one and the same
method throughout, by which step by step, knowledge per-
fects itself — at one time by discovering errors, at another
by correcting them ; and if at certain stages in this pro-
gress difficulties seem insuperable, we can gain nothing by
calling in, even provisionally, the aid of any sort of Eidolon,
whether "cell," "protoplasm" or internal principle.

It thus appears to be doubtful whether any of the
biological writers who have recently professed vitalistic
tendencies are in reality vitalists. The only exception
that I know is to be found in the writings of a well-
known morphologist, Dr. Hans Driesch,1 who has been
led by his researches on what is now called the Me-
chanics of Evolution to revert to the fundamental con-
ception of vitalism, that the laws which govern vital
processes are not physical, but biological — that is, peculiar
to the living organism, and limited thereto in their
operation. Dr. Driesch's researches as to the modifi-
cations which can be produced by mechanical inter-
ference in the early stages of the process of ontogenesis
have enforced upon him considerations which he evidently
regards as new, though they are familiar enough to Physio-
logists. He recognises that although by the observation of
the successive stages in the ontogenetic process, one may
arrive at a perfect knowledge of the relation of these stages
to each other, this leaves the efficient causes of the develop-
ment unexplained [fukrt nicht zu einem Erkenntniss ihrer
bewirkenden Ursacheii)- — it does not teach us why one

1 Driesch. " Entwicklungsmechanische Studien " : a series of ten
Papers, of which the first six appeared in the Zeitsch. /. w. Zoologie, vols,
liii. and lv. ; the rest in the Mittheihingen of the Naples Station.

LUDWIG AND MODERN PHYSIOLOGY. 21

form springs out of another. This brings him at once face
to face with a momentous question. He has to encounter
three possibilities — he may either join the camp of the
biological agnostics and say with du Bois-Reymond, "ignora-
mus et ignorabimus" or be content to work on in the hope
that the physical laws that underlie and explain organic
Evolution may sooner or later be discovered, or he may
seek for some hitherto hidden Law of Organism of which
the known facts of Ontogenesis are the expression, and
which, if accepted as a Law of Nature, would explain every-
thing. Of the three alternatives Driesch prefers the last,
which is equivalent to declaring himself an out and out
vitalist. He trusts by means of his experimental investiga-
tions of the Mechanics of Evolution to arrive at " elementary
conceptions" on which by "mathematical deduction"1 a
complete theory of Evolution may be founded.

If this anticipation could be realised, if we could con-
struct with the aid of those new Principia the ontogeny of
a single living being, the question whether such a result
was or was not inconsistent with the uniformity of Nature,
would sink into insignificance as compared with the
splendour of such a discovery.

But will such a discovery ever be made ? It seems to
me even more improbable than that of a physical theory
of organic evolution. It is satisfactory to reflect that the
opinion we may be led to entertain on this theoretical
question need not affect our estimate of the value ol Dr.
Driesch's fruitful experimental researches.

J. Burdon Sanderson.

1 " Elementarvorstellungen . . . die zwar mathematische Deduktion
aller Erscheinungen aus sich gestatten mochten." Driesch. " Beitrage
zur theoretischen Morphologic" Biol. Centralblatt, vol. xii., p. 539, 1892.

ON RECENT ADVANCES IN VEGETABLE

CYTOLOGY.

PART I.

DURING the last quarter of a century a considerable
change has passed over the aspect of biology,
especially in this country. It was formerly possible for a
man to be, fairly at any rate, well up in the two branches
of zoology and botany, but this is no longer possible,
regarded from our modern standpoint. Specialisation,
inevitable owing to the rapid advances which have been
everywhere made, has not only effected a practical
divorce between these two sciences, but the same disrupting
agency is operating continuously in each of them.

None the less is it true, however, that there are certain
features of fundamental importance which are shared alike
by animals and plants. This community of structure is
most clearly recognised within the limits of the individual
cells, and it is perhaps nowhere more impressively demon-
strated than in the remarkable similarity which exists
between the nuclear division as observed in animals and in
plants, — a similarity which may extend to the most minute
details.

The cell, using the word in its widest sense, is, as
Haeckel said long ago, emphatically the unit of life. For
though the several parts, such as nucleus and the cell-
protoplasm, which together constitute a cell, all possess
autonomy to a certain degree, it still remains true that it is
only when they operate jointly and in harmony that a suc-
cessful and "going concern," a living individual, is the
result. And since we have strong reasons for believing
that animals and plants represent the diverging limbs of a
stock traceable at the root to a common source, viz., lowly
unicellular organisms, it is obvious that the study of the cell,
of its structure and of the functions discharged by its
various parts, offers an immensely important, though it
may well be a very difficult, field for research.

RECENT ADVANCES IN VEGETABLE CYTOLOGY. 23

What, we may ask, is the essential structure of the
protoplasm, of the nucleus, and of those marvellous bodies,
the chromosomes, which reappear at every nuclear division ?
What is it that initiates the division of a cell or of its
nucleus, and why do some cells go through such complex
evolutions whilst others seem to adopt a relatively simple
course? What is it that determines that the descendants of
one cell shall develop differently from those of another, so
as to give rise to this or that tissue system ? Or again,
how is the unicellular condition of an infusorian compatible
with an intricate and often highly differentiated organisa-
tion ?

These and a host of other questions rise and confront
us on the very threshold of our inquiry, and the hints which
Nature has dropped for our guidance are at best only
obscure ones ; thus the position of the biological investigator
contrasts unfavourably with that of the chemist or physicist,
inasmuch as he is generally debarred, owing to the very
conditions of the bodies he is dealing with, from having
recourse to direct experiment ; Nature conducts the experi-
ments and he has to remain content with watching- the
result, analysing the factors and reconstructing the process
as best he can. Nevertheless there is, clearly, no funda-
mental distinction between the (so-called) observational
and experimental sciences.

It is, then, only by patient accumulation and careful
comparison of all the facts that even a proximate solution
of the difficulties before us can ever be reached. Much
has been done in collecting the data, and a good deal is
known both as to the structure of the cell and the phases
through which it passes during its existence. And fortu-
nately one generalisation is gradually emerging with in-
creasing clearness from beneath the ever-growing pile of
detail, and it promises to prove a guide of no small value,
namely, that in those processes which we have reason to
regard as fundamentally important there exists a surprising
degree of similarity between the structural elements of
animals on the one hand and of plants on the other. And
these points of similarity are now known to be so numerous

24 SCIENCE PROGRESS.

and so close that we are almost warranted in drawing the
conclusion that the measure of the resemblance will afford a
criterion as to the relative degree of importance to be
attached to this or that phenomenon of cell life.

It seems almost certain that this similarity is to be
interpreted as the result of the evolution along parallel
lines of a particular structural arrangement, or, to put it in
another way, as being the outcome of the continuous opera-
tion of similar forces upon an essentially similar proto-
plasmic structure. No doubt all the change manifested in
protoplasm is ultimately to be ascribed to the effects of
forces upon its own material substance ; the special point
of interest here lies in the similarity of the results. It
cannot be due to mere accident that the stages in the develop-
ment of the spermatozoa of a newt should bear a closer
resemblance to the corresponding divisions in the pollen-
mother-cell of a lily than they do to the rest of the tissue
cells in the body of the same newt.

In the present article it is not my purpose to attempt to
summarise the vast amount of detail which has accumulated
within recent years ; my aim is rather to try to indicate the
general directions in which the results seem to be tending,
and to point out the kind of evidence on which the current
views are based. And although I am here especially dealing
with the botanical aspect of the questions involved, it will
be clear from what has been already said that it will be
impossible, and certainly not desirable, to ignore the in-
vestigations which have been prosecuted by the zoologists.

And in order to make clear that which is to follow, it
may not be superfluous to recapitulate the general relations
of nucleus and cell protoplasm as commonly received at the
present time. The essential character of all cells, whether
animal or vegetable, and whether they exist as free inde-
pendent organisms, or whether they form more or less
highly differentiated colonies, consists in this, the association
of a nucleus with a certain amount of cell protoplasm (com-
monly called Cytoplasm, to distinguish it from the nuclear
protoplasm). And this is equally true, so far as we have
means of determining the question, in the case of those

RECENT ADVANCES IN VEGETABLE CYTOLOGY. 25

organisms in which we as yet have failed to recognise a de-
finite nuclear body, for there are reasons for believing that the
nuclear substance is in all cases really present, whether it
happens to be collected into a specialised mass or not. And
it should be remembered that the number of cells supposed
to possess what we may term a distributed or discrete
nucleus is becoming smaller as our means of investigations
improve. Thus according to Wager ( 1 ) even Bacteria
possess a true nucleus.

I am perfectly aware that attacks have recently been
made on the cell-theory as extended to explain the organisa-
tion (Whitman, Sedgwick) of animals, and that nobody
would assert the cell to the ultimate unit of living substance.
But neither of these propositions really affects, or is con-
cerned with, the point of view just now before us. We are
not here dealing with the wide questions connected with the
architecture of the organism as a whole, nor with the
equally difficult one, as to what constitutes the ultimate
units of living matter, rather we are content just now to
study the interaction of the parts which together are capable
of carrying on a continuous living existence, which form a
living individual, and these parts consist jointly of the
nucleus and its surrounding cytoplasm.1 The occurrence of
cell walls is a matter of no importance from a general stand-
point, although when present they may profoundly modify
the characters of the organism in which they are formed.
Many plants are known in which the protoplasm is only
delimited by a cell wall from the surrounding medium, while
the oftentimes huge protoplasmic mass suffers no internal
partitioning, although it contains a vast number of nuclei
distributed through it.

Sachs, with characteristic insight, long ago perceived
that the presence or absence of cell walls is a matter of
only secondary importance. Their sequence and arrange-
ment at the time of their first appearance can be predicted

1 The researches of Klebs, Acqua, and others have shown that although
protoplasm deprived of a nucleus may sometimes even assimilate food and
maintain life for a not inconsiderable period of time, it is incapable of
division.

26 SCIENCE PROGRESS.

from simple geometrical considerations quite independently
of the ultimate form which will be finally assumed as
the result of specialised growth. And in applying the word
Non-cellular to those plants in which partition walls do not
occur, he merely gives formal expression to the fact that
these anatomical structures are absent, although in other
respects the plants in question conform with those usually
called multicellular, and they are not at all to be regarded as
consisting of a single enlarged cell. In fact he has expressly
stated that non-cellular plants are really the equivalent of
multicellular organisms in which the formation of internal
cell walls does not occur. More recently he has introduced
the term Energid (2) to express the physiological individu-
ality of those units I have here continued to call cells, and
he thereby emphasises the fact of their real existence
whether any positive anatomical boundaries can be dis-
cerned between them or not.

It must however be clearly understood that in formulat-
ing the expression energid, Sachs lays especial stress on
the dynamical aspect of the relations existing between the
cytoplasm and the nucleus. But it will be admitted by most
people that a conception of force apart from the material
substance on or through which it acts, and by which its
operation becomes perceptible to the senses, belongs to the
domain of purely abstract ideas. We require to know far
more of the nature and structure of protoplasm before we
can usefully divorce our conceptions of force from our ex-
perience of matter in attempting to ascertain the nature
of those physiological causes of which all external form is
but the outward and visible sign. Sachs himself, however,
escapes the charge of vagueness, by restricting the applica-
tion of his expression so as to impose a territorial limit to
the sphere of influence mutually existing between each
nucleus and the surrounding cytoplasm. For him the word
Energid embodies the idea that the whole protoplasmic
region is partitioned into smaller provinces each dominated
by its own nucleus. And although it may be advantageous
for the seprovinces to be delimited from each other by cell
walls, permitting thereby a more complete independence to

RECENT ADVANCES IN VEGETABLE CYTOLOGY. 27

attach to each one severally, the existence of such well-
defined boundaries is by no means an indispensable condition
of great complexity of organisation. Caulerpa amongst the
algae imitates very closely the differentiated form of some
of the higher terrestrial plants, without however possessing
their corresponding internal structure. Its protoplasm is
bounded by an external wall only, and is not internally
partitioned. And yet the characters distinctive of the
energids in the leaf-like parts are assuredly different from
those of the energids which exist in the creeping stem or
rootlike fibres. A transition from the condition of Caulerpa
to that of the higher plants may be seen in Cladophora, in
which the filamentous body seems, at first sight, to be made
up of chains of cells, each of which stands in a definite
relation to the general symmetry of the branched plant ;
nevertheless, closer examination shows that each "cell" is
multi-nucleate, and really represents a federation of energids
which so act together as to constitute morphological units as
far as the external form of the plant as a whole is concerned.
Sachs' conception of the energid has been assailed by
some writers, and he has to some extent perhaps invited
criticism by formerly affixing a quasi-morphological, as well
as a physiological significance to the term. At first sight
it may seem difficult to justify its application in those cases
in which streaming movement happens to go on in certain
layers of the protoplasm, whilst the layer in which the
nuclei are embedded is at rest. It is obvious that if we
admit, as we can hardly avoid doing, that the nucleus does
really exert a directive action over a localised area, the
migratory protoplasm (assuming the movement to affect the
protoplasm, and not merely the granular bodies contained
in it) must be constantly coming within the range of
fresh centres of influence. It may perhaps be compared
to the case of a person passing from a region presided
over by one government into one under the jurisdic-
tion of another. Such a person would naturally be subjected
to changed conditions, without however affecting either his
own identity or that of the particular political centres through
which he may happen to travel.

28 SCIENCE PROGRESS.

Strasburger (3) has attempted to define more clearly the
position of the individual energid, by proposing to limit its
application to the nucleus together with a special part of the
cytoplasm which he calls Kinoplasm and which he regards
as the proximate seat of the effective manifestation of the
forces at work in the cell. He regards the nomadic
streaming protoplasm as being mainly charged with the
function of providing nourishment for the nucleus and
kinoplasm, and he distinguishes it by the special term of
Trophoplasm. Strasburger maintains this same distinction
between the active Kinoplasm and the nutritive tropho-
plasm in those cases in which the limits of the several
energids correspond with those of the individual cells ;
and in this he is logical enough, for we know that living
cells are not isolated from each other, but that protoplasmic
continuity exists between adjacent cells by means of pores
in the intervening walls. How far the distinction between
kinoplasm and trophoplasm is either justified by observa-
tion or demanded by theory is another matter altogether.

But although the conception of energids is a happy one,
as enabling us to distinguish discrete individualities in what
may at first sight appear to consist of a common structure,
it is not to be inferred that the individuals enjoy independ-
ence. The great merit of the idea lies in the fact that it
serves to narrow down, and hence to render more clearly
comprehensible, many important problems which call for a
solution before we can hope to grapple successfully with
the more advanced questions relating to those forces of a
still higher order which control and apparently direct the
development of the organism as a whole, or to put it in
another way, which determine the course of development
which the particular energids shall follow. Such control is
plainly apparent at every stage in the life of an organism.
Why does growth take place symmetrically so that the
energids, cells, or whatever we may choose to call them, so
act in unison as to produce a " body fitly joined together
and compacted by that which every joint supplieth, accord-
ing to the effectual working in the measure of every
part " ? Without some such assumption how is it

RECENT ADVANCES IN VEGETABLE CYTOLOGY. 29

possible to account for the fact that in certain embryos
which have been mutilated, the surviving cells are enabled
to so modify the course of their normal development as
to make good the loss, and thus to form a perfect, if
somewhat miniature organism ? For had there been no
mutilation the cells thus concerned would unquestion-
ably not have developed in the same way, but would have
fulfilled the allotted task of merely providing for the genesis
of their normal tissue products. Or again, why is it that
when a lizard's tail is broken off the general form of the
entire animal is once more reproduced, even though there
are important histological and structural (but probably not
functional) differences in the new tail as compared with
that of the original one (4) ?

When differentiation has so far become manifested in
an organism that the limits of the several energids are
coterminous with the cell walls, a considerable increase in
their degree of independence doubtless ensues, but it is, as
already stated, by no means absolute, and the examples just
quoted support the statement. Whether organisation is
the result of, or the factor which determines, the co-ordi-
nate action of the cells is a question which we may safely
leave to the future to decide. But perhaps it may be
permissible to compare the cell colony which forms the
organism to an isolated society in which the caste system
prevails. Each caste or cell group is predestined to dis-
charge certain definite offices in the state or the organism.
If some indispensable caste should become exterminated, it is
obvious that a differentiation and displacement must occur
amongst those which survive, and this differentiation
might either be readily complete, or it might only arise as
a reluctant concession to necessity, just as a willow twig
planted upside down in damp soil will form roots at this, its
upper, end ; though comparison with a twig planted with
its basal end in the ground will show how severe a tax the
unusual effort has proved.

It has already been said that an energid, and it might
also be added, a typical cell, consists essentially of a nucleus
and the protoplasm included within a certain area around

30 SCIENCE PROGRESS.

it. But we cannot as yet answer the more obvious and, one
might think, almost preliminary question as to what the
chief functions which are discharged by these two com-
ponents really may be. It is certain that the existence of a
nucleus is essential to morphological development such as is
implied in the production of new cells, and very probably
also in the further differentiation of those which have
already been formed. Instances of this are seen for example
in the growth or alteration of the cell wall. Haberlandt
(5) some years ago drew special attention to the fact
that when local thickening occurred in a cell wall the
nucleus commonly moved to this spot, and the present
writer has repeatedly observed it during the formation of
the hard coat found on many seeds ; here the deposition of
substance is usually localised on the inner parts of the cell,
and the nucleus takes up a corresponding position as soon
as the process begins. Korschelt (6) has observed a
similar relation to exist during the chitinisation of the mem-
branes of insect cells, and quite recently Istvanffi (Ber. Deut.
Gesel., Dec, 1895) has observed that when the tubular
hypha of Mucor branches, a nucleus is invariably present at
the spot whence the branch is arising. Strasqurger (3^) has
also drawn attention to the same truth, inasmuch as he
states that before the opening of the zoosporangium of
CEdogonium, the nucleus and kinoplasm aggregate in the
vicinity of the spot at which the hole is about to be formed.

But perhaps one of the most striking instances of the
directive effect of the nucleus as a whole is to be seen in
the result of an experiment of Boveri, who asserts that he
impregnated a non-nucleated piece of protoplasm of an
echinoderm ovum with the sperm nucleus of another species ; 1
development ensued, and the larva resembled the paternal
form (7).

In discussing the relations which exist, or are supposed
to exist, between the cytoplasm and the nucleus, it is clearly
of the first importance to know what are the changes which
occur in them, and especially in the nucleus, during the

1 The animals actually employed were Echinus microtuberculatus
(male), and Sphaerechinus granulans (female).

RECENT ADVANCES IN VEGETABLE CYTOLOGY. 31

growth, maturity and senescence of the cells. Some ex-
tremely interesting results in this direction have recently been
published by Zacharias (8). An ordinary resting nucleus
consists, as all biologists are aware, of a somewhat dense
thread-like framework, often spoken of as linin, which
usually exhibits copious anastomosis, sometimes to such a
degree that it almost forms a spongy texture. In this
framework granules are found embedded which react
definitely to stains and to solvents ; they constitute the
nuclein, a phosphorus-containing substance which at the
periods of nuclear division undergoes an enormous increase
in bulk. The linin is bathed in a more fluid substance, the
paralinin. One or more spherical bodies, the nucleoli,
are often present in addition to the foregoing constituents,
and the nucleus is delimitated from the cytoplasm by a
pellicle or membrane. The nucleolus contains, as was
shown by Zacharias many years ago, at least two
substances, one of which is of an albuminous nature, and is
dissolved out on treatment with gastric juice ; after peptic
digestion has extracted the albumin, a substance is left
which Zacharias calls Plastin. Now observation shows
that the relative proportion of these two constituents varies
considerably at different periods of the life of the cell, and
this is of importance in connection with the intricate series
of changes which the nucleus passes through during the
process of ordinary division. The conviction has slowly
been forced upon us within the last few years that there
exists a considerable variety amongst the bodies which
have been included in the common term of nucleoli.
Auerbach (9) showed in 1890 that some of them
absorbed certain red dyes with greater avidity than they did
certain blue ones, whilst other nucleoli reacted in the oppo-
site manner. He thus distinguished between erythrophil
and cyanophil nucleoli. These results have been extended
to plants by the investigations of Rosen (10) and others,
but especially by Zacharias, who has applied the test of
solvents to them, with the result that the difference between
the two classes of nucleoli proves to be a much more real
one than had hitherto been supposed. And these observa-

32 SCIENCE PROGRESS.

tions are specially interesting when considered from the
point of view of the great dissentience of opinion which exists
between most botanists and zoologists as to the nature and
function of the nucleolus. Strasburger, who admitted the cor-
rectness of Rosen's statements, considered that the difference
between an erythrophil and a cyanophil nucleus was largely
one of nutrition, and he instanced in support of his view
the difference between the erythrophil nucleolus in the
nucleus of the well-nourished oosphere and the cyanophil
nucleus of the much smaller, and therefore presumably
worse nourished generative cell of the pollen tube. But
Zacharias, in criticising Strasburger's views, considers that
there is no evidence to prove that the one nucleolus is in a
better position than another as regards its nutrition, and it
is still more difficult to accept the suggested explanation in
those cases in which both forms of nucleoli are concomi-
tantly present.

Zacharias has shown that whereas the erythrophil
nucleoli contain albumin and plastin, the cyanophil kind
(the "pseudo-nucleoli" of Rosen and others) contain nuclein,
a substance quite absent from the other class of nucleoli.
Rosen in 1892 stated his conviction that his pseudo-nucleoli
in reality consisted of chromatic substance (nuclein) and
that they contribute to the formation of those remarkable
bodies, the chromosomes, which are evolved by the break-
ing up of the linin framework after the amount of nuclein
has greatly increased in it, previous to the division of the
nucleus. Now the nucleolus exhibits striking chancres both
during the growth, and also during the division of the cell and
its nucleus. As regards the behaviour during cell growth, the
relation of the nucleolus to theothercomponents of the nucleus
is highly suggestive, and seems to support the view of those
who hold that its function is largely, at any rate, nutritive.

In the embryonic tissue situated at the growing points
of plants, the cells are all much alike, differentiation and
specialisation only taking place behind these regions.
Consequently it is possible to trace the changes which a
cell exhibits during its transition from a primitive state to
its adult form, and often, further, through the various stages

RECENT ADVANCES IN VEGETABLE CYTOLOGY. 33

of senescence and death. Some cells, indeed, are not really
useful to the plant of which they form a part, until they are
dead, i.e., till the wall of the cell alone remains, whilst from
its cavity the protoplasm has disappeared.

The researches of Zacharias and of Rosen, which have
recently been published, were directed especially to the
behaviour of nuclei in the apical regions of plants, and
their results in the main are confirmatory of each other,
though the two observers were interested in rather different
aspects of the same problem. The nuclei of all actively
dividing cells are markedly cyanophil, and this character is
especially noticeable just below the active generative cells.
At first sight it may seem remarkable that in a fern root
the nucleus of the large apical cell is less cyanophil than
are the nuclei of the dividing segment cells which have
been cut off from it. But the anomaly is only apparent,
for though all the cells in the root owe their origin ulti-
mately to the division of the apical cell, it must not be
forgotten that the nuclear divisions in the segments which
are cut off from it are far more frequent. The segments
divide up into a very large number of cells before they
finally form permanent tissue cells, and therefore it is not
surprising to find that the nucleus of the apical cell, which
is the ancestor of them all, contains less nuclein than the
more actively dividing descendants. But there are several
other significant observations which go to show that in cells
which are in a state capable of further division, this faculty is
correlated with the presence of nuclein in their nuclei. Rosen
found in the roots of the bean and other flowering plants
that after the tissues were beginning to show differentiation,
the zone of cells forming the pericycle1 retained, in their
nuclei, the characters of embryonic cells, that is to say,
that, whereas the nuclei of the rest were losing their cyano-
phil character and were becoming erythrophil, the pericyclic
•nuclei retained their nuclein contents. . Now the lateral
roots arise in this pericyclic layer, and they do so by the
differentiation in it of new growing points. Hence these

1 A zone of parenchymatous cells sheathing the more central wood and
bast parts of the vascular strand.

3

34 SCIENCE PROGRESS.

new rootlets can only be developed from cells which still
retain, or can re-awaken, embryonic characteristics. Be-
hind the region in which lateral roots arise, the cells of
the pericycle lose their cyanophil nature, and here again
the loss is first apparent in those cells from which, even
normally, no roots would originate, viz., those situated
opposite the phloem. It would be interesting to know
whether in the case of those roots in which the lateral
rootlets arise right and left of the protoxylem (e.g., Cruci-
ferse) a corresponding difference obtains.

Again, Zacharias noticed that during the development
of the guard-cells of the stomata in a number of leaves
a similar difference held good. In a simple case, e.g.,
many Liliacese, the mother-cell of the guard-cells is cut
off from a cell which is destined at once to form one of the
ordinary and relatively large epidermal cells. In this case,
whilst the nucleus of the mother-cell of the stoma retains
its nuclein contents, the other one rapidly becomes poorer
in this constituent, it grows and develops a large nucleolus.
The small mother-cell again divides to form the guard-cells
of the stoma, and only then does a nucleolus become at all
conspicuous, and the nuclein diminish in quantity. And
therewith the further capacity for division ceases.

Besides the connection which is shown to exist between
a nucleus which is capable of division, and its richness in
nuclein, there are certain other facts of importance which
demand notice. The nuclei of cells which are actively
dividing are commonly characterised by the possession of
smaller nucleoli than are those in which no further divisions
will take place, but which are still growing in size. In fact
Zacharias states generally that, as regards nuclei of cells
emerging from the meristem region, the nucleoli first
increase to a maximum, that this is accompanied by an
enlargement of the nucleus as a whole, which however only
reaches its maximum size after the nucleolus has done so,
and that the latter body then diminishes faster than does
the nucleus as a whole.

Further, Zacharias found that not only is the nucleolus
losing substance in those cells which are specialising to

RECENT ADVANCES IN VEGETABLE CYTOLOGY. 35

form tracheids, vessels and sieve tubes, but that the nucleus
as a whole is losing, and still more rapidly, those substances
which are capable of being removed by peptic digestion
from the cell. The facts seem to suggest that it is albumin,
or some other proteid, which is disappearing ; and it is
clear that the loss is due to a change in the nucleus itself,
irrespective of the amount of nutrition available in the
surrounding plasma, since the change is extremely obvious
in the degenerating nuclei of sieve tubes, in spite of
the fact that they are surrounded by abundant albuminous
substances in the slimy contents of the cells. On the other
hand, in those cells which are growing in size, preparatory
to further divisions, such as in spore-mother-cells, the
increase in albuminous substances, both in the nucleus
generally, and especially in the nucleolus, is strongly marked.
Spore-mother-cells, as a rule, pass through a relatively long
period of growth, and hence we might perhaps anticipate
(as we find to be the case) that they exaggerate the changes
seen in the dividing and growing cells of the apical meri-
stem. But I do not wish to lay too much stress on this,
because we know that other, and profound, changes occur
during the growth of spore-mother-cells, and it is uncertain
to what extent the facts just mentioned may be connected
with them.

It may possibly be objected that observations like those
of Zacharias are open to adverse criticism on the ground that
the chemistry, and a fortiori the microchemistry, of the
proteids and other substances which occur in cells is as yet
in such an unsatisfactory condition. But this objection is
really not a legitimate one. We know that certain struc-
tures in the cell are differentiated by their selective action
on certain dyes, and it is to this fact that their recognition
was due in the first instance. But we find the action of
certain solvents to yield no less definite results. Given a
nucleus in a particular condition (as judged by the structure
rendered visible by staining), and it will be found that the
degree of solubility of its constituent substances is charac-
teristic for the particular stage in the life history of the cell
or of the nucleus which may happen to have been selected.

36 SCIENCE PROGRESS.

Hence it seems clear that the two methods ought both to
be employed ; for whilst the staining exhibits more or less
completely the structural arrangement of the substances
present, the microchemical method not only indicates some
at least of the important differences which exist between
the different structures revealed by the action of staining,
but it teaches us that certain of these same structures are by
no means so homogeneous in their nature as one might be
led to suppose relying on the evidence derived from stain-
ing alone.

But those who pin their faith on stains sometimes seem
to forget that they are after all only employing a sort of
microchemical method themselves. For the fact that
different histological elements of the cell are distinguishable
by stais, implies the existence of a chemical dissimilarity
between them. And this becomes the more obvious when,
owing to periodically recurring changes in the cell, we
assert that this or that structure is growing or diminishing.
The investigator who is consciously proceeding on micro-
chemical lines is at least not so open to the charge of mere
empiricism as are those who look for salvation to
haematoxylin or the anilin dyes. He may be wrong in
supposing, for example, that the phosphorus within the
nucleus only occurs in the nuclein, just as he may be in
error in assuming that the substance nuclein itself really re-
presents a chemical substance in the same way that sugar
does. But he materially advances our knowledge of the
cell when he determines the fact that a body which fluctuates
in size as does the nucleolus, is composed of two substances
or groups of substances one of which is soluble in gastric
juice whilst the other is not ; and that further, the relative
size is, in the first instance, correlated with the amount of
substance which the fermentative action of pepsin can render
soluble.

It is readily conceded that the bodies we call nuclein,
plastin, and the like, possibly may not, as stated already,
represent chemical molecules at all. This does not, how-
ever, diminish the interest attaching to the proof that this
or that substance is at one time present, while at another

RECENT ADVANCES IN VEGETABLE CYTOLOGY. ^

time it can be no longer recognised in its former place.
Nor does this observation lose in importance when the
differences are shown to closely accompany changes in the
general characters of the cells themselves.

BIBLIOGRAPHY.

(i) WAGER, H. Preliminary Note on the Structure of Bacterial
Cells. Annals of Botany, vol. ix.

(2) Von Sachs. Physiol. Notizen II. Flora, 1892. Also

Physiol. Notizen IX. Flora, Erganzungs bd., 1895.

(3) STRASBURGER. Ueber d. Wirkungssphare d. Kerne u. d.

Zellgrosse. Histologische Beitrdge, v., 1893.
(3«) STRASBURGER. Schwarmsporenjgameten.Pflanzlichen sperm-
atozoiden, und das Wesen d. Befruchtung. Hist. Beitr., iv.,
1892.

(4) Boulenger, G. A. On the Scaling on the Reproduced Tail

in Lizards. Proc. Zool. Soc, 1888.

(5) HABERLANDT, G. Ueb. d. Beziehungen Zwischen Function

u. Lage d. Zellkerns b. d. Pflanzen. Jena, 1887.

(6) KORSCHELT. Beitrager 2. Morph. u. Physiol, d. Zellkerns.

Zool. Jahrb., 1889.

(7) BOVERI. Ein Geschlechtlich erzeugter Organismus ohne Mtit-

terliche Eigenschaften. Sitzungsber. d. Gesellsch. f. Morph.
u. Physiol, zu Miinchen, 1889.

(8) ZACHARIAS, E. Ueb. d. Verhalten d. Zellkerns in Wachsenden

Zellen. Flora, Erganzungs bd., 1895.

(9) AUERBACH, L. Zu Kentniss d. Thier. Zellen. Sitzungsber. d.

Kgl. Preuss. Akad. d. Wissensch., 26th June, 1890.
(10) ROSEN, F. Ueb. tinctionelle unterschied verschied. Kernbes-

tandtheile u. d. sexualkerne. Colitis Beitr. z. Biol. d. Pflanzen,

v., 1892.
(iOtf) ROSEN, F. Beitr. z. Kentniss d. Pflanzenzellen. Colitis

Beitr., vii., 1895.

J. Bretland Farmer.

THE MORPHOLOGY OF THE MOLLUSCA.

^> H E recent publication of a number of new manuals and
monographs dealing with the Mollusca offers a favour-
able opportunity for a review of our knowledge of this
great phylum of the animal kingdom. It is not fifteen
years since Professor Lankester's classical article on Mollusca
was published in the Encyclopedia Britannica, yet the con-
tributions to Molluscan morphology since that date have
been not only numerous, but in many cases of prime im-
portance.

The older method of inquiry, that of the comparison of
types more or less arbitrarily selected from different groups,
has been succeeded by investigations more directly in-
fluenced by the idea of evolution. The comparison of types
has been replaced by the study of groups. The founda-
tions of the morphological edifice were laid upon the former
method ; the superstructure and details are the result of
the latter. Homologies having been to a large extent
determined, we now seek phylogenies. It happens also
from time to time that the detailed study of a group with
the object of reconstructing the phylogeny of its members
leads occasionally to the discovery that homologies based
on the simple method of anatomical comparison turn out
to be nothing more than analogies — recurrent examples of
similar modifications.

One result of these phylogenetic inquiries has been the
concentration of particular attention upon forms which are
presumably the most primitive in each group ; and great
advances have thus been made in our knowledge. Kow-
alewsky and Marion, Pruvot, Wiren, and Thiele have
enormously extended our acquaintance with the Apla-
cophorous Isopleura ; primitive Prosobranchs (Docoglossa
and Rhipidoglossa) have been thoroughly investigated by
Haller and Boutan ; Bouvier has thrown new light upon the
Opisthobranchia by his researches on Actceon ; Boas and
Pelseneer have revolutionised our ideas of the Pteropoda

THE MORPHOLOGY OF THE MOLLUSC A, 39

by their work upon Limacina among the Thecosomata, and
upon Dexiobranchcea and other types among the Gymnoso-
mata ; the morphology of the Pelecypoda has been further
elucidated by Pelseneer's observations upon Nucula and
other primitive forms, and important contributions to our
knowledge of the Cephalopoda were made during the past
year by Huxley and Pelseneer in the case of Spirilla, that
last survivor of the ancient types of Decapod Dibranchiates.
We doubt if any equivalent group of the animal kingdom,
except perhaps the Echinoderma, has been the subject of
such productive researches as the M ollusca during the period
under consideration ; and certainly the phylogenetic method
of inquiry has attained no greater triumphs than in the
hands of Bouvier, Haller, Pelseneer, and other inves-
tigators of the Gastropod and Lamellibranch series.

In the present article I propose to deal more especially
with recent contributions to our knowledge of the Molluscan
nervous system, reserving a fuller consideration of other
questions for a later article.

There is one writer, however, whose views must first of
all be dealt with, as on a great number of fundamental
points they are opposed to all current conceptions of
Molluscan morphology. These views merit some detailed
consideration, moreover, for they are based on propositions
which are not without a certain appearance of plausibility,
and may well serve as test-questions by which to examine
into the accuracv of the homologies which have been
generally admitted to exist between the different sections
of the Molluscan phylum.

Thiele has published his views in a series of lengthy
papers, the references to which will be found in the biblio-
graphy (23, 24, 25). He regards the Mollusca and Anne-
lida as direct descendants of Polyclad Turbellarians, and
his identifications of homologous organs in the different
Molluscan groups are determined, not by a direct comparison
of the organisation of these types one with another, but
by independent comparisons of the organisation of the
different Molluscan types with that of sucker-bearing
Polyclads. The group Mollusca is thus made to lose its

40 SCIENCE PROGRESS.

compactness, and characteristic organs, such as mantle and
ctenidium, which have been regarded as homologous
throughout the Molluscan series, are interpreted in different
ways in the different types, as the exigencies of Thiele's
theory demand. One of the first propositions assumed by
this writer is that the foot of the Mollusca is simply a colossal
enlargementof the ventral sucker of the Polyclad; thesuctorial
function of the foot in Chiton and the lower Gastropoda is
pointed to in support of this comparison. A series of
more revolutionary propositions is then promulgated in
consequence of the necessity under which the author is
placed of discovering the primitive body-edge of the
Mollusca comparable to the edge of the body of the Tur-
bellaria. This primitive body-edge Thiele identifies by
means of the lateral sense-organs which characterise the
epipodium in the Rhipidoglossa and the margin of the
mantle in Pelecypoda. The epipodium in Gastropoda and
the mantle edge in Pelecypoda are thus taken by this writer
to represent the sides or edge of the body in the Tur-
bellarian ancestor. The epipodium in Gastropoda and the
mantle edge in Pelecypoda consequently separate the
dorsal from the ventral regions of the body in those groups.
It follows from this that the ctenidia of Gastropoda, which
are supra-epipodial in position, are not homologous with
the ctenidia of Pelecypoda, which are infra-pallial. How we
are to regard the anus, which is dorsal in the one group and
ventral in the other, is not explained. But since in oper-
culate Rhipidoglossa the operculum, like the shell, is
situated above the epipodium, we are told that the oper-
culum must also be regarded as dorsal in position, as well
as serially homologous with the shell proper. This, in
Thiele's eyes, compares well with the condition of affairs in
Chiton, whose shelly plates are without doubt serially
homologous. Moreover, although the existence of an
epipodium in Chiton has not been hitherto recognised,
Thiele argues that, since the pallial fold in this form re-
presents the primitive body-edge, it must also, together with
the series of ctenidia which are attached to its lower surface,
be regarded as the homologue of the epipodium of the

THE MORPHOLOGY OF THE MOLLUSC A. 41

Rhipidoglossa. The ctenidia of Chiton are, in fact, re-
garded as modified epipodial cirri. The consequence of
this view is that while the mantle of Chiton and the mantle
of Pelecypoda are regarded as homologous, the mantle of
the Gastropoda is supposed to represent only a portion of
the mantle in these other forms, and its projecting rim,
similar as it appears to be in the two cases, is held to be a
new and secondary formation unrepresented in the Am-
phineura and Pelecypoda.

Nowhere, however, do we find in Thiele's voluminous
writings any explanation of the anomaly which ought to
have occurred to him, that while in Chiton the anus is
"ventral," and lies well beneath the "epipodium" and the
last shell-plate, in operculate Gastropods the intestine opens
not only above the epipodium, but between the operculum
and the shell of the embryo — a relation which could only be
represented in Chiton, if Thiele's theories were correct, by
the situation of the anus between two of the shell-plates
upon the back of that animal !

The nervous system of the Mollusca is treated by Thiele
with a ruthlessness no less than that which is meted out
to the external organs of the body. Let us take the
Amphineura first. In this group, if the relations of the
nervous system in Chiton be taken as typical, we have
dorsal to the gut a great ganglionic nerve-ring whose lateral
components are usually referred to as the lateral or pleuro-
visceral cords. Connected anteriorly with the cerebral
enlargements of this nerve-ring is a pair of ventral or pedal
cords, connected with one another by a series of commis-
sures lying beneath the gut, and also with the lateral cords
by means of lateral connectives. The lateral cords inner-
vate the pallial sense-organs, gills, and viscera ; the ventral
cords the musculature of the foot. The lateral cords are
regarded by Thiele as the homologues of the lateral cords
or nerve-ring of the Turbellarians. and the ventral cords are
taken to correspond to the ventral longitudinal nerves of
the same forms. So far we find nothing either erratic or
original, for the same view has already been taken by Lang

(16).

42 SCIENCE PROGRESS.

But the novelties begin with Thiele's interpretations of
the nervous system of Gastropoda and Pelecypoda. We
have already pointed out Thiele's view that the epipodium
of Gastropods represents the primitive body-edge. Now
at the base of the epipodium in Fissurella and Haliotis there
lies a ganglionic plexus ; and this plexus, which takes the
form of an incomplete ring, is regarded as the homologue
of the lateral cords of Turbellarians and Amphineura. The
series of epipodial nerves which connect the epipodial plexus
with the upper half of the pedal cords in Rhipidoglossa is
compared with the series of connectives between the lateral
and ventral cords in Amphineura.

This seems very plausible until one recollects (i) that,
the epipodium being infra-rectal, the epipodial plexus is
also infra-rectal and thus difficult to compare with the
lateral cords of Amphineura, whose "commissure" is supra-
rectal ; and (2) that, whereas in Amphineura the lateral
cords innervate practically the whole of the pallium and
viscera, in Rhipidoglossa the epipodial plexus has nothing
to do with any other organs except the sense-organs of the
epipodium. If the pallium of the Gastropoda is really, as
Thiele maintains, a secondary differentiation of the primary
pallium of the Amphineura, one would expect that its
innervation would also be effected by progressive differen-
tiation of the nerve-centres which supplied the primary
pallium, viz., from the lateral or epipodial centres. So far
from this being the case, however, Thiele himself (xxv., pp.
587-9) adopts the view that the pallial nerves as well as the
pleural ganglia of Gastropoda are secondary derivatives of
the ventral or pedal cords.

The recklessness of Thiele's comparisons reaches its
high-water mark, perhaps, in his remarks on the nervous
system of Pelecypoda. Correlated with the existence of
numerous sense-organs (eyes, tentacles, etc.) along the
mantle edge, there exists in many forms {Area, Pecten,
Pinna, etc.) a nervous ring around the mantle which may
take the form either of a complete ring of peripheral ganglia
united by a plexus, or of a circumpallial ganglionated nerve,
as was recognised by Duvernoy (5) more than thirty years

THE MORPHOLOGY OF THE MOLLUSC A. 43

ago. Since the mantle-lappets of the two sides of the body
unite posteriorly above the anus, this pallial nerve-ring lies
above the gut. The ring is connected with the cerebro-
pleural ganglia by means of the anterior pallial nerves, and
with the visceral (parieto-splanchnic) by means of branches
from the great posterior pallial nerves. Accordingly Thiele
homologises the circumpallial nerve-ring with the lateral
cords of Chiton and with the epipodial plexus of the Rhi-
pidoglossa.

The first of these homologies seems not unreasonable, for
no one disputes the homology between the mantle of Chiton
and that of Pelecypoda. Moreover Kowalevsky's discovery
that Chiton in its later embryonic phases is provided with
a pair of transitory eyes which lie outside the velar area
and have some close connection with the lateral nerve-
cords, renders this comparison particularly worthy of
attention. But how the circumpallial nerve of Pelecypoda
can be in any sense homologous with the epipodial plexus
of Gastropoda, when the latter structure lies beneath the
gut and has no connection with the cerebral ganglia, either
directly or by the intermediation of the pleural ganglia, it
is altogether impossible to conceive. And this is not all.
The posterior connection between the circumpallial nerve
of Pelecypoda and the visceral ganglia is compared by
Thiele with the posterior connectives between the lateral
and ventral cords of Amphineura ; and the time-honoured
visceral nerve-cords of Pelecypoda, with the visceral (parieto-
splanchnic) ganglia upon them, are homologised with the
ventral cords of the Amphineura. To reveal the absurdity
of these comparisons it is sufficient, I think, to remind my
readers that the ventral cords of Chiton are concerned ex-
clusively with the innervation of the musculature of the
foot ; while the visceral cords of Pelecypoda innervate
the body-wall, ctenidia and viscera^ in addition to the
posterior adductor muscle. How these supposed homo-
logues of the ventral cords of Chiton have come to assume
so many of the functions of the lateral or pallio-visceral
cords, is not explained ; and since Pelecypoda possess a
pair of pedal ganglia in the foot, as typical in their relations

44 SCIENCE PROGRESS.

as those of any Gastropod — in Nucula to the extent even
of having separate cerebro-pedal and pleuro-pedal connec-
tives (18, 19) — it seems profitless to pursue these ill-
balanced speculations any further.

The utmost ingenuity cannot overcome the fact that
there is a fundamental disparity between the Turbellarian
and Molluscan body. This disparity is revealed by em-
bryology ; but to embryology Thiele pays scant attention.
Thiele's argument is practically this (24, p. 504), — that
the only route from Ccelenterates to Bilateralia is via the
Ctenophores to Polyclads, and that Annelids and Molluscs
are consequently to be derived from Polyclad ancestors.
Embryology seems to me, however, to point to two lines of
descent at least, from the Ccelenterates to the Bilateralia.
In each case the oral surface of the Ccelenterate ancestor
became the ventral surface of the Bilateral descendant ; but
along one line of descent the primitive mouth or blastopore
retained its ancestral form as a simple circular orifice in the
middle of the ventral surface, and opened into a gastral
cavity devoid of an anal orifice (Polyclads) ; while along the
line of descent which led to the Annelida and Mollusca the
blastopore elongated along the ventral surface, as Sedg-
wick has so ably contended, its lips coalesced except at the
two extremities, and these open ends constituted the mouth
and anus of the Ccelomate descendants. Thiele has
altogether overlooked the significant behaviour of the blas-
topore in Annelidan and Molluscan embryos ; and since
no similar modification of the blastopore is known in the
case of Turbellarians and Trematodes, in which groups the
absence of an anus is so marked a characteristic, we are
amply warranted, I think, in drawing the conclusions which
I have emphasised above.

The admission of this distinction is however fatal to
any theory of the Polyclad ancestry of the Mollusca. The
foot of the Mollusca is a development of the fused lips of
the elongated blastopore, and can in no case be homo-
logised with the ventral sucker of Turbellarians which lies
entirely behind the blastopore. The same remark applies
to Lang's comparison of the Molluscan foot with the ventral

THE MORPHOLOGY OF THE MOLLUSC A. 45

surface of the Turbellarian. The foot is undoubtedly part
of the ventral surface of the Mollusc, and as such may be
compared, in a general way, with the creeping surface of a
Planarian ; but as a specialised organ, developed from the
fused lateral margins of a slit-like blastopore, it has no
homoloeue in the organisation of the Turbellaria.

Let us now see what light has been thrown on the
problems of Molluscan morphology by the researches of
other investigators.

The visceral commissure. — One of the greatest dif-
ficulties in comparing the Amphineura with the Gastropoda
or other Molluscan types has long been the fact that the
lateral or pleuro-visceral cords of Chiton, which innervate
the gills, viscera, and mantle, are united to one another
posteriorly by a "commissure" lying above the rectum;
whereas the visceral commissure of Gastropoda and Pelecy-
poda, etc., lies below the intestine.

A little care in the use of words would have prevented
much of the confusion and controversy which has arisen on
this subject of the position of the visceral commissure.
Words, as Bacon phrases it, put constraint upon the in-
tellect, and there is no doubt that the disagreement and
perplexity of naturalists concerning this point have been
caused by one of the idola fori which they have themselves
set up, rather than by any intrinsic incompatibility in the
facts themselves. If the language must still be maintained,
I must at least point out that there are commissures and
commissures, and that one may be a commissure in fact,
and another only in name. The suprarectal ''commissure"
in Amphineura is ganglionic, and, like the rest of the
pleuro-visceral nerve-ring, is formed in situ by delamination
from the ectoderm (15). It is not a commissure in the
strict sense of the word, but an integral portion of an
annular central nervous system. But the visceral loop of
other Molluscs consists merely of nerve-fibres connecting
usually a couple of visceral ganglia with one another, and
with the pleural ganglia. Now nerve-fibres are outgrowths
from nerve-cells, and if two groups of nerve-cells should
happen to take a somewhat deep-seated position in the body

46 SCIENCE PROGRESS.

before their fibres have grown out (which is not a rare
embryological phenomenon), there should be nothing in-
comprehensible in their fibres taking the shortest route and
meeting beneath the gut instead of over it. Clearly, there-
fore, the ventral position of the visceral commissure in
most Mollusca by no means precludes the possibility of the
essential homology between the visceral loop of these
forms and part of the pleuro-visceral ring of Amphineura.

The other differences between the visceral loop of most
Mollusca and the pleuro-visceral ring of Amphineura are-
principally differences in the degree of segregation and
concentration of ganglion-cells and nerve-fibres. The
pleuro-visceral ring of Chiton represents a very primitive
nervous system, characterised by the more or less even
diffusion of ganglion-cells over the whole length of the
cord, while the nerves arising from it are not united into
large trunks, but are given off at repeated intervals in a
manner which is almost metameric. The nerves springing
from it innervate the same parts of the body as the com-
bined pleural and visceral ganglia of Gastropods and other
Molluscs, viz., mantle, ctenidia, intestine, heart, nephridia,
and gonads. But if, after the reduction of the ctenidia to
a single pair, we imagine a process of segregation to set in
between these various elements, the more strictly visceral
centres would become separated from the superficial pallial
centres, and would assume a deeper position in the body.
The law of concentration would apply in this as in other
cases of evolution of nervous systems (3), and the result of
the whole process would be the differentiation of a visceral
nervous system, consisting of ganglia and commissural
fibres, out of the primitively mixed and diffuse pleuro-visceral
system. If the primitive relations to the gut and ring-like
form were retained at all, they would be retained, not
necessarily by the visceral system, which has ex hypothesi un-
dergone considerable changes, but by the pallial (= pleural)
system, which has undergone no change, except possibly
one of incipient concentration.

The position of the commissural fibres of the visceral
ganglion in relation to the gut becomes a matter of sub-

THE MORPHOLOGY OF THE MOLLUSC A. 47

ordinate importance if the evolution of the nervous system
has proceeded upon these lines, as will be made evident
later on. As a matter of fact the visceral commissure is
situated below the gut — a relation which is possibly fore-
shadowed in Chiton by a connection beneath the gut of the
two gastric nerves described by Haller (8).

Pelseneer (19) indeed goes so far as to identify these
gastric nerves of Chiton with the visceral commissure of
Gastropoda and Pelecypoda; but the considerations which I
have emphasised above show that the typical visceral nerves
and commissure have not yet arisen in the Amphineura ;
they do not arise, in fact, until the branchial, nephridial,
genital and enteric branches of the primitive pallio-visceral
cords are all united into one common trunk. There is
some doubt, moreover, as to the existence of the gastric
nerves described by Haller, since two investigators, Plate
(20) and Thiele, have been unable to discover them in
species of Chiton examined by themselves.

A valuable contribution to this part of the subject is
contained in Haller's recent Studien (11). In the
common cyclobranchiate types of Limpet the pallial nerves
are separate from one another behind, and seem to be
mere outgrowths of the pleural ganglia (Bouvier, 3, p. 19);
but in Lottia, one of the more primitive monobranchiate
forms, Haller shows that the pallial nerves of the two sides
are directly continuous with one another posteriorly, and make
a complete arch round the edge of the mantle. They are
moreover not mere nerves, since they consist of a core of
fibres surrounded by an outer coating — discontinuous, it is
true — of ganglion-cells. They are clearly the posterior
continuations of the pleural ganglia, and represent the re-
mainder of the pallio-visceral nerve-ring of the Amphineura
after the separation of the visceral elements. This view is
further borne out by the existence of several connectives
between the pallial ring and the pedal cords in addition to
the stout ganglionic connective which in higher forms
becomes the persistent pleuro-pedal connective.

The pleural ganglion. — Haller's discovery recorded in
the preceding paragraph shows clearly the error of the

48 SCIENCE PROGRESS.

view by which the pleural ganglion is regarded as a
derivative of the pedal cords (Bouvier, Pelseneer, etc.,
passim). This view is founded on the fact that in the lower
Gastropoda (Docoglossa and Rhipidoglossa) the pleural
ganglia are directly continuous with the anterior ends of
the pedal cords, while in the higher types the pleural ganglia
gradually move further and further away from the pedal
ganglia, and, travelling along the cerebro-pleural connectives,
eventually come into contiguity with the cerebral ganglia
(Tenioglossa) or even fuse with them to form a single
cerebro-pleural ganglion on each side (Pelecypoda).

The close connection between the pleural and pedal
ganglia in the lower forms may now be interpreted
in a different manner. The ganglion-cells which were
primitively distributed over the whole extent of the pallial
nerve-ring have been concentrated at the anterior ex-
tremities of its lateral portions, as Haller's observations
on Lottia show— or rather in the reo-ion of the first
pleuro-pedal connective, for the most anterior portion of
the primitive pallial cords is represented by the cerebro-
pleural connective. The shortness of the pleuro-
pedal connecting piece and the great concentration of
ganglion-cells which takes place at its two extremities
prevent any sharp demarcation between the pleural and
pedal ganglia in these lower forms ; but a comparison of
the nervous system of Lottia with that of Chiton (Thiele,
2 3 ? P- 387) leaves no room for doubt as to the correct-
ness of this interpretation, which throws a flood of light
upon numerous other points which have been difficult to
understand upon the older views. It explains, for example,
why the cerebro-pleural and cerebro-pedal connectives
should be already distinct from each other in the lower
Gastropods at a stage when the pleural ganglia are in
actual continuity with the pedal cords, and it sets at rest
the controversy as to the meaning of the lateral furrow
in the pedal cords of Rhipidoglossa which has been waged
with so much skill in the rival pages of the Archives de
Zoologie and the Bulletin Scientifique de la France et de la
Belgique.

THE MORPHOLOGY OF THE MOLLUSC A. 49

Development of the pleural ganglion. — That the pleural
ganglion is essentially distinct from the pedal is, I think,
sufficiently clear from the facts of development. Although
these ganglia are placed so close together and are so inti-
mately connected in the lower Gastropods there is not a
single case on record in which the pleural ganglion has been
observed to arise from the pedal ganglion, or from a
common pleuro-pedal rudiment in the embryo. It is
equally true on the other hand that Sarasin's derivation of
the cerebral and pleural ganglia from a common rudiment
in Bithynia (the cephalic sense-plate) has been opposed by
v. Erlanger, who shows that all the great ganglionic centres
arise separately, and do not become connected with one
another until after their differentiation (7).

A renewed investigation of the origin of the cerebro-
pleural ganglion in Pelecypoda would be of great interest
in this connection. Pelseneer's ( 1 8) observations on Nuctila
have placed the fact of the composite nature of this ganglion
in Pelecypoda beyond all doubt ; and still, to the best of
my knowledge, no one has yet observed the appearance in
the embryo of a pleural element distinct from the main body
of the ganglion. This apparent community of origin of the
cerebral and pleural ganglia in Pelecypoda may be compared
with the direct continuity of the cerebral and pleural
elements of the nervous system in Amphineura.

Development of the visceral ganglia. — Sarasin en-
deavoured to show that the visceral ganglia of Bithynia,
together with the pedal and abdominal ganglia, arise in the
embryo from a common ventral proliferation of the ectoderm
which he compares with the ventral ganglionic chain of
Annelida. On this point also Sarasin has been corrected
by v. Erlanger, who shows that all these ganglia arise
separately from one another in Bithynia (7), as well as in
Palndina (6).

The visceral ganglia are also quite distinct from the
pleural ganglia in their origin, as v. E Hanger's observations
show. In one important respect, however, the visceral
ganglia and the pleural ganglia betray a marked similarity,
the significance of which seems, however, to have escaped

4

50 SCIENCE PROGRESS.

the attention of its discoverer. In Paludina v. E danger
figures the pleural ganglia arising from the ectoderm on
each side of the body at a point just outside the velar area,
but in actual contiguity with the cells of the ciliated ring.
In Bithynia (7, Taf. xxvi., fig. 16) he figures the same
condition of things for the pair of visceral ganglia. The
only difference in origin between the two ganglia is that the
visceral ganglia arise behind the pleural ganglia. If the
Molluscan veliger possessed a nerve-ring beneath its proto-
troch (velum), as occurs in the trochosphere of the Annelida,
it is quite clear that the pleural and visceral ganglia of
Bithynia and Paludina would represent a series of gangli-
onic thickenings along the course of the nerve-ring. Apart
from this inference, however; the topographical relations to
which I have called attention seem sufficient to establish
the proposition that the pleural and visceral ganglia, and,
as I shall show directly, the abdominal ganglion also, of
Gastropods — and, therefore, of other Mollusca — belong to
a group of dorso-lateral nerve-centres quite distinct from
that which is represented by the ventral or pedal cords.
Here again we are reminded of the direct continuity of the
pleural and visceral nerve-centres in the Amphineura.

Development of the abdominal ganglion. — In Chiton,
as Kowalevsky has shown (15), the unpaired abdominal
ganglion, or, as it is often called, the visceral ganglion,
arises by a proliferation of the ectoderm at the hinder pole
of the embryo, dorsally to the site of the future proctodeum.
In the adult this ganglion is simply a special concentration
of ganglion-cells on the supra-anal portion of the pleuro-
visceral ring.

The abdominal ganglion of Gastropods is also situated
at the hinder end of the visceral loop, but lies of course
ventral to the gut. Can these two ganglia be regarded as
homologous ?

If Molluscs were mere mechanical models the answer
would be undoubtedly in the negative ; but embryology
points unhesitatingly to the opposite conclusion. Von
Erlanger has shown that in Bithynia as well as in Paludina
the abdominal ganglion develops as an ectodermal pro-

THE MORPHOLOGY OF THE MOLLUSC A. 51

liferation of the floor of the mantle-cavity, i.e., that the
ganglion is essentially a dorsal ganglion. Its final situation
on the course of the sub-intestinal nerve-loop is rendered
possible by the fact that its connectives with the visceral
eanolia are not delaminated from the ectoderm, as are the
ganglionic pleuro-visceral cords of Chiton, but are mere
fibrous outgrowths from the ganglia themselves. Embry-
ology is thus in complete accord with the views which have
been maintained in the earlier part of this paper as to the
homologies and origin of the visceral nervous system in
Mollusca.

The pallial and visceral commissures in Cephalopoda.
— It has long been known (Hancock) that in many Cepha-
lopoda the stellate ganglia on the pallial nerve-cords are
connected with one another above the gut by a transverse
commissure. Is this commissure a relic of the pallio- visceral
nerve-ring of the Amphineura and homologous with the
pallial ring of Lottia, or is it merely a secondary connection ?

In Spirilla a remarkable arrangement of the pallial
commissure has been recognised by Huxley and Pelseneer
in their recent memoir (12). The commissure is not in
this case a straight transverse band, but consists of two
curved cords which arise from the right and left stellate
ganglia respectively, and at their junction in the median
line of the body give off a median pallial nerve which runs
for a short distance forwards, and then passing over the
anterior margin of the shell — which is, of course, internal —
becomes recurrent and runs along the part of the mantle
contained within the last chamber of the shell. Pelseneer is
thus led to regard the commissure with its median nerve as
formed by the two original pallial nerves fused together.
The connection between the stellate ganglia having thus
arisen in the primitive Dibranchiates (apparently in con-
nection with the reduction in size and enclosure of the
chambered shell), higher forms show a series of stages in
its subsequent degradation, until it is finally lost in the
Octopoda. The absence of a pallial commissure in Nautilus
also supports Pelseneer's view that in Cephalopoda this
structure is not of any primary importance.

52 SCIENCE PROGRESS.

At the same time when Pelseneer added a paragraph to
the effect that the supra-rectal commissure of the Amphi-
neura is also a merely secondary junction of the pallial
nerves, he was probably not yet acquainted with Haller's
work on Lottia, and allowed his views upon the Polychsete
ancestry of the Mollusca to bias his interpretation of the
Molluscan nervous system.

In a recent paper on the anatomy of Nautilus Mr.
Graham Kerr (13) also refers to the question of the supra-
rectal commissure. It will be remembered that in Nautilus
the pleuro-visceral ganglia of the two sides form a stout
ganglionic band encircling the oesophagus in the region of
the cerebral ganglia. The pallial nerves radiate from the
lateral portions of this half-ring, and the pair of visceral
nerves arise from the ventral portion. The visceral cords
pass backwards on either side of the vena cava, and, after
giving off the branchial nerves, are prolonged posteriorly as
far as the post-anal papilla, behind which Mr. Kerr has
recognised an apparent anastomosis. Mr. Kerr adds that
in this case " the homologue of the pleuro-visceral cord of
Chiton is not merely the posterior sub-cesophageal nerve-
mass, but rather the two lateral portions of this, together
with the post-branchial prolongations which run on either
side of the vena cava. The mesial part of the posterior
sub-cesophageal nerve-mass would therefore be a secondary
fusion between the nerve-masses of the two opposite
sides."

In his suggested homology of this possible post-anal
{i.e., supra- rectal) commissure of the visceral nerves in
Nautilus with the supra-rectal " commissure " of Chiton,
Mr. Kerr has undoubtedly failed to appreciate the true
nature of the posterior sub-cesophageal loop of Nautilus, as
well as the relation of the visceral nerves to the pleuro-
visceral cords of Chiton. The explanation of the Cephalo-
pod nervous system is most readily found by comparing it
with that of Dentalium, whose organisation in many respects
supplies connecting links between that of the Cephalopoda
and that of the primitive prae-torsional Gastropod or
primitive Pelecypod. In Dentalium (22, p. 401) we find

THE MORPHOLOGY OF THE MOLLUSC A. 53

a pair of post-anal prolongations of the visceral nerves
precisely resembling those described by Kerr in Nautilus ;
yet in Dentalium, owing to the smaller degree of concen-
tration or cephalisation which has taken place in the
nervous system, it is easy to see that the typical sub-intes-
tinal visceral commissure exists as in Gastropods and
Pelecypods. The posterior sub-cesophageal nerve-mass
of Cephalopods has clearly been produced, not, as Mr.
Kerr suggests, by a secondary fusion of the pleuro- visceral
nerve-masses of the two opposite sides, but by a simple
shortening of the visceral loop as it occurs in Dentalium.
This would bring the visceral ganglia into continuity
with the pleural ganglia and with one another, — a process
of condensation with which we are already familiar in the
Tenioglossa and the Euthyneura among Gastropoda.

It may here be mentioned that Willey's simultaneous
account (26) of the visceral nerves of Nautilus, while con-
firming Mr. Kerr's observations as to the existence of post-
anal prolongations of a pair of visceral nerves, differs from
his statement as to their origin. Willey states that the
nerves supplying the post-anal papilla arise independently
from the sub-cesophageal visceral loop, although at their
origin they are adjacent to the branchial nerves and for a
large part of their course are actually contiguous with them.
The significance of this separation is not remarked upon by
Willey ; but if the separation really exists it is certainly a
difficulty in the way of his contention that the post-
anal papilla represents an approximated posterior pair of
branchial sense-organs, since the anterior osphradium and
both gill-plumes are all innervated from the outer visceral
nerve.

Etithyneurism. — Since the publication of Spengel's paper
on the olfactory organ and nervous system of Mollusca, a
division of the Gastropoda into two groups, the Strep-
toneura and the Euthyneura, has been generally adopted.
This classification has been accepted, moreover, not merely
as an expression of the anatomical facts concerning the
condition of the visceral loop in the two groups, but as a
classification of phylogenetic significance. It is to be in-

54 SCIENCE PROGRESS.

ferred that the two groups have been independently derived
from a common type of archi-Gastropod, possessing an un-
twisted visceral loop — the Prosobranchs (Streptoneura) by
the twisting of the loop, the Opisthobranchs and Pulmonates
(Euthyneura) by the mere shortening and concentration of
the untwisted loop. This view derives support from the
fact that the persistent ctenidium retains its primitive posi-
tion on the right side of the body in Opisthobranchs, while
in Prosobranchs it shows a marked displacement and lies
on the left side. Bouvier's observations on Actceon
( = Tornatella), however, have completely altered the posi-
tion of affairs. Actceon is a very primitive Opisthobranch,
as may be inferred from the high development of its shell,
the persistence of its operculum, and the absence of pleuro-
podial fins. Bouvier tell us (4) that Actcson resembles the
Prosobranchs, not only in these points, but also in possess-
ing a distinct twist of the visceral loop (streptoneurism,
chiastoneurie). The ctenidium is innervated from a supra-
intestinal ganglion, which lies on the left side of the body.
We are accordingly led to the conclusion that the
euthyneurous condition of Opisthobranchs and Pulmonates
has not been directly inherited from the orthoneurous
ancestors of the Gastropoda, but has been derived from a
previously streptoneurous condition. In other words the
Opisthobranchs and Pulmonates have descended from
Prosobranch ancestors, and the right-sided position of the
gill-plume in Opisthobranchs is not primitive, but the result
of a secondary process of detorsion.

Orthoneuroidism. — Without going further into the
matter it may also here be mentioned that the supra-in-
testinal commissure has been recently discovered in various
species of Nerita, Neritina, and Navicella by Boutan (2),
Bouvier (3^), and Haller (11) — a discovery which de-
stroys the last refuge of orthoneurism in Prosobranchiate
Gastropods. Streptoneurism may now be affirmed of all
Prosobranchiate Gastropods.

Origin of the Moliuscan nervous system. — The attempts
of previous writers to explain the relations of the nervous
system of Mollusca have been based almost exclusively

THE MORPHOLOGY OF THE MOLLUSC A. 55

upon comparisons with the fully constituted nervous
systems of such types as the Turbellaria and Annelida.
With Thiele's theory of the Turbellarian ancestry of the
Mollusca I have already dealt, and I do not propose to
deal with the Annelidan hypothesis, since this theory can-
not provide any satisfactory explanation of the high develop-
ment of the pleuro-visceral nervous system of the Mollusca.
Those authors who, like Thiele and Pelseneer, homologise
both the pleural and pedal centres of the Mollusca with the
ventral cords of Annelids, base their view upon the sup-
posed origin of the pleural centres from the pedal cords.
This derivation I have already shown in this article to be
completely erroneous. Pelseneer's theory of the origin of
the Mollusca from Polychsete ancestors (18a), and all
theories which seek the origin of the Mollusca in the
specialised representatives of any of the vermiform groups,
may at once in my opinion be dismissed from considera-
tion.

Apart from matters of minor importance it will, I think,
be conceded that the following cardinal points in regard
to the morphology of the Molluscan nervous system have
been established by the facts and arguments which have
been presented in this article : —

(1) That the pleural ganglia have not been derived by

segregation from the ventral or pedal cords.

(2) That the pleural, visceral, and abdominal ganglia

of Gastropoda form a group of dorsal nerve-
centres — the two former owing to their dif-
ferentiation in the immediate neighbourhood of
the velum, and the latter owing to its differentia-
tion from the mid-dorsal wall of the body (floor
of mantle-cavity).

(3) That the dorso-lateral nerve-ring of Amphineura

is primitive and is represented in other groups
of Mollusca by both the pallial and visceral
nerve loops, or their derivatives.

(4) That the sub-intestinal position of the visceral loop

in all groups except the Amphineura is a
secondary one, which has been rendered possible

56 SCIENCE PROGRESS.

only by the decentralisation of the primitive
pleuro-visceral nervous system, and its separa-
tion into special ganglia and nerves, the latter
being formed ontogenetically as fibrous out-
growths from the ganglionic centres.
Venturing now, in conclusion, upon more speculative
ground, I believe that the embryonic relations, to which I
have drawn attention, between the pleural and visceral
ganglia and the ciliated band are of phylogenetic importance.
It has long puzzled me that the larval forms (trochospheres) of
two groups so closely allied as the Annelida and Mollusca,
while presenting a close similarity in general structure,
should differ so remarkably in regard to their nervous
system. The Annelid trochosphere has a nerve-ring
beneath its ciliated band, while the Molluscan trocho-
sphere has none. In this respect the Molluscan trocho-
sphere appears to be less primitive than that of the
Annelida. The explanation of this now appears to me to
be as follows. In the evolution of the Annelida the proto-
troch and nerve-ring remained for a long time unmodified,
and did not share in the elongation of the postero-ventral
region of the body which gave rise to the trunk of the
Annelid. This would explain the absence of the dorsal
nerve-ring in the adult Annelid, provided that the nerve-
ring, together with the prototroch, came to have merely a
larval significance, — as actually happens in the ontogeny of
Annelids to-day. On the other hand, in the evolution of
the Mollusca from the same simple type of ancestor, the
whole body must have shared in the elongation — the proto-
troch and nerve-ring as well as the more ventrally placed
parts of the body. This elongated nerve-ring I identify
with the pleuro-visceral ring of Amphineura, although the
phyletic connection between the nerve-ring and the ciliated
band is inferred from the development of certain Gastro-
pods rather than from the Amphineura themselves. As a
larval adaptation for conveniences of natation I imagine
that a separation became gradually effected in embryonic
life between the ciliated ring and the nerve-ring, the former
becoming restricted to the anterior end of the larval body,

THE MORPHOLOGY OF THE MOLLUSC A. 57

while the latter became more and more extended pari passu
with the elongation of the trunk. Such a separation is to
some extent paralleled in the development of Holothurians
from the Auricularia larva, as described by Semon. On
this theory alone can I explain to myself the absence of the
ancestral nerve-ring in the trochospheres of Mollusca, and
I find some support for this view in the ontogeny of Nemer-
tines. The lateral nerve-cords in this group have the same
relation to the gut and brain as have the pleuro-visceral
cords of Chiton, since they form a dorso-lateral ring, the
posterior commissural portion passing above the rectum.
In Nemertines there can be very little doubt that this
nerve-ring has been derived phyletically by the elonga-
tion of a nerve-ring which underlay the ciliated band of a
more or less Pzlidzum-like ancestor, as it underlies the
ciliated band of the Pi/idzum-laxva., although this phyletic
origin is disguised by the profound metamorphosis which
breaks the continuity of the ontogenetic record in Nemer-
tines. On this theory of course the lateral cords of Nemertines
do not correspond to the ventral cords of Annelids. The
latter are represented by the general ventral plexus of
Nemertines and by the pedal plexus or cords of Mollusca.
These ventral nervous systems appear to bear relations to
the dorso-lateral ring-nerve similar to those of the subum-
brellar plexus of Medusae to the circumferential nerve-ring.
It will be recognised from these remarks that the
conclusions to which I have arrived present distinct points
of agreement with those of Balfour (1, p. 37&) and Sedg-
wick (21) on the same subject, although attained throughout
by an independent series of inductions. With both these
writers I agree in tracing back the Molluscan nervous
system to a primitively annular type, such as might be
expected to exist in a Ccelenterate ancestor. Balfour
derives the whole Molluscan nervous system from a
peripheral nerve-ring which followed the course of a hypo-
thetical ciliated ring: ; Sedgwick derives it from a broad
plexus surrounding an elongated blastopore, such as occurs
in existing Actinians. Sedgwick's theory was practically
an alternative to Balfour's, but I find myself able to give a

5» SCIENCE PROGRESS.

partial acceptance to both these views. For the nervous
system of Mollusca appears to me to consist of two parts, a
circumferential ring and a peri-blastoporal plexus. The
circumferential ring, which was primitively associated with
a ciliated ring, is represented by the pleuro-visceral nervous
system, which I have shown to possess significant relations
with the velum or prototroch of the larva ; and the peri-
blastoporal plexus seems to me to be recognisable in the
pedal nervous system, which in primitive Molluscs has a
very diffuse plexus-like arrangement, and in Amphineura,
at any rate, reveals its peri-blastoporal character in the
cerebro-pedal connectives in front and its connectives with
the supra-rectal abdominal ganglion behind.

BIBLIOGRAPHY.

(i) Balfour, F. M. Comparative Embryology, ii., 1885.

(2) BOUTAN. Arch. Zool. Exp. (3), i., pp. 221-265, 1893.

(3) Bouvier. Systeme Nerveux des Prosobranches. Ann. Sci.

Nat. (7), iii., 1887.
{id) Bouvier. Comptes Rendus, cxiv., p. 1281, 1892.

(4) BOUVIER. Comptes Rendus, cxvi., pp. 68-70.

(5) Duvernoy. Mem. sur le systeme nerveux des Mollusques

Acephales. Mem. Acad. Sci. Paris, xxiv.

(6) ERLANGER, R. von. Zur Entwicklung der Paludina vivipara,

I. u. II. Theil. MorpJi. Jahrbuch, xvii., 1891.

(7) ERLANGER, R. VON. Zur Entwicklung von Bithynia ten-

taculata. Mitth. Zool. Stat. Neapel. x., 1892.

(8) HALLER, BELA. Die Organisation der Chitonen der Adria.

Arb. Zool. Inst. Wien, 1882-3.

(9) HALLER, BeLA. Untersuchungen Liber marine Rhipido-

glossen, I. Morph.Jahrb., ix., 1884.

(10) Haller, Bela. Die Morphologie der Prosobranchier. Morph.

Jahrb., xiv., 1888.

(11) HALLER, BELA. Studien liber Docoglosse u. Rhipidoglosse

Prosobranchier, 4I-0, 1894.

(12) HUXLEY and PELSENEER. Report on Spirula. "Challenger"

Reports, Zool, part lxxxiii., Appendix, 1895.

(13) KERR, J. G. On some Points in the Anatomy of Nautilus

pompilius. Proc. Zool. Soc, part iii., 1895.

(14) Korschelt u. Heider. Lehrbuch der Entwicklungs

geschichte, iii., 1893.

THE MORPHOLOGY OF THE MOLLUSC A. 59

(15) KOWALEVSKY, A. Embryogenie du Chiton polii. Ann. Mus.

Hist. Nat. Marseille., Zool., i., 1883.

(16) LANG, ARNOLD. Lehrbuch der Vergl. Anat, 3 heft.

(17) Lankester, E. Ray. Mollusca. Encycl. Brit., ninth

edition.

(18) PELSENEER. Contribution a l'etude des Lamellibranches.

Arch, de Biol., xi., p. 166, pi. vi., fig. 3, 1891.
(i8#) PELSENEER. Classification Generale des Mollusques. Bull.
Sci. France et Belg., xxiv., p. 346, 1892.

(19) PELSENEER. Introduction a l'etude des Mollusques. Bruxelles,

1894.

(20) PLATE. Bemerk. lib. d. Phylogenie u. d. Entstehung d.

Asymmetrie d. Mollusken. Spengel's Zool. Jahrbiicher, Abth.
f. Anat. u. Ont., ix., i., p. 169, 1895.

(21) Sedgwick, Adam. On the Origin of Metameric Segmenta-

tion. Quart. Jour. Micr. Sci., xxiv., 1884.

(22) SlMROTH. Bronn's Klassen u. Ordnungen des Thier-Reichs .

Mollusca. I. Amphineura u. Scaphopoda, 1892-94.

(23) Thiele, J. Ueber Sinnesorgane der Seitenlinie und das

Nervensystem von Mollusken. Zeit.f. IViss. Zool, xlix., pp.
385-432, 1890.

(24) Thiele, J. Die Stammesverwandschaft der Mollusken. Jena

Zeit., xxv., p. 480, 1 89 1.

(25) Thiele, J. Beitrage zur Kenntniss der Mollusken. Zeit. J.

Wiss. Zool, liii., p. 578, 1892.

(26) WlLLEY, A. Natural Science, vi., p. 412, 1895.

Walter Garstang.

THE RESERVE MATERIALS OF PLANTS.

( Concluded. )

THE position of the glucosides in vegetable metabolism
has been for a long time a subject of considerable
controversy, which has, however, been most largely con-
cerned with tannin. The details of its formation, its locali-
sation and its fate have been discussed at great length, but
the discussion has been largely conducted on the lines of
hypothesis and analogy rather than experiment. The con-
clusions reached by such a method of treatment have some-
what hastily been applied to all glucosides, as if tannin were
eminently the typical one. There are now reasons for
thinking that so far from this being the case it is especially
exceptional.

The number of oflucosides known has increased con-
siderably in recent years as our investigations into plant
metabolism have been pursued, and increasing knowledge
of them forces the conviction more and more upon us that
they take a more or less active share in the nutritive pro-
cesses, possibly direct, but more probably through certain
of the products to which they give rise on decomposition.
They are not so markedly reserve stores for seeds as are
many of the bodies we have already discussed, though many
seeds, and notably many of those of plants of the Rosaceae
and Cruciferse and orders allied to these, contain them in
quantity together with other reserves. They occur, how-
ever, in other parts of the plant, not quite as circulating
reserves, but rather as transitory stores for more localised
growth and nourishment. The old advocates of their
nutritive functions rested their case largely on the presence
of sugar in the glucoside molecule, and held that this is the
body which is available for the constructive processes of the
organism. There are, however, reasons for holding that
this view is too limited a one. and that some of the other
products of their decomposition may be as valuable as the
sugar, if not of even greater importance.

THE RESERVE MATERIALS OF PLANTS. 61

The glucosides that have attracted most attention during
recent years are those which occur in the plants belonging to
the families already mentioned, the Rosacese, the Cruciferae,
and other orders which show affinities with these. These
plants contain, very widely distributed through their tissues,
amygdalin and sinigrine or myronate of potash respectively.
Of these the former is perhaps the most interesting, as
from its decomposition by enzyme agency there is produced
hydrocyanic acid, which has always been regarded as most
virulent in its action upon all living things. The existence
of this noxious principle in the plant has perhaps been partly
the cause of the readiness of botanists to class the glucoside
which yields it, and hence the whole class of glucosides,
among the products of excretion.

The localisation of the amygdalin is calculated to throw a
good deal of light upon the question of its probable function
and fate. For many years attention has been given to it,
at first, owing to imperfect methods of research, without
much practical result. Improvement in technique has,
however, yielded very valuable results, and has led to
conclusions greatly at variance with those held thirty
years ago. Thome (60), who wrote in 1865 upon the
nutritive materials contained in the sweet and bitter al-
monds respectively, said that amygdalin occurs in the
parenchyma of the cotyledons of both varieties, and that
its corresponding enzyme, emulsin, is only present in the
bitter almond, being localised in the weak fibrovascular
bundles that are in the cotyledons. This statement has
been shown to be the exact converse of the truth. Portes
(61), who worked twelve years later, showed that the gluco-
side and the enzyme occupy different parts of the seed, the
former being distributed in the cotyledonary parenchyma,
while the latter is to be found in the axis of the embryo.
Pfeffer (62), in his Pflanzenphysiologie, suggests that this
localisation is not accurate, and that the two bodies probably
occupy the same cells, the only degree of separation being
that the ferment is in the protoplasm and the glucoside dis-
solved in the cell-sap. In 1887 Johansen (63) by chemical
methods succeeded in ascertaining the distribution of the

62 SCIENCE PROGRESS.

two bodies in the seeds. He found the emulsin to be pre-
sent in both varieties of the almond, and to be chiefly
localised in the fibrovascular bundles. He further ascer-
tained that the glucoside, amygdalin, is only present in the
cotyledonary parenchyma of the bitter one. The absence
of the glucoside from the seed of the sweet almond points,
of course, to the conclusion that even if it be a nutritive
body it is not one of very great prominence in the nutrition
of the embryo on germination.

Guignard has published within the past few years a
series of researches which deal primarily with the localisa-
tion of the enzymes which decompose the glucosides, but
which incidentally throw a certain light upon the occurrence
and meaning of the latter. In his first papers (64) he treats
of the amygdalin which is found in the almond and in the
cherry laurel, in the latter of which it is found to have a
fairly copious distribution. He confirms Johansen as to its
position in the seed of the almond, and still more closely
localises the enzyme. In the laurel (Prunus lauro-cerasus)
the parenchyma of the leaves as well as of the axis appears
to contain it in solution in the cell-sap. The occurrence of
the emulsin is confined to the neighbourhood of the con-
ducting- tissues, it being chiefly found in the endodermis
round the fibrovascular bundles. In the bundles of the axis
of the embryo in the almond the ferment occurs in the many
layered pericycle, chiefly outside the bast. The distribution
of the amygdalin is not definitely known. It may happen
that the fluid sap containing it may travel along the cellular
tissue, and the occurrence of the ferment which decomposes
it, in the immediate neighbourhood of the conducting tissues,
suggests that it is charged with the duty of preparing from
the glucoside certain nutritive products that may easily make
their way to the conducting tissues, and so travel to the
actual seats of constructive metabolism. That sugar so
travels is of course a matter of every-day experience, but
whether or no the remaining products are made use of in a
similar way is open to discussion. On the other hand it
may be that the amygdalin descends by the conducting
tissue of the bast and undergoes decomposition as it passes
downwards, yielding simpler products to the young cortex.

THE RESERVE MATERIALS OF PLANTS. 63

In the face of the problem of the utilisation of the bodies
resulting from the action of emulsin upon amygdalin great
importance must be ascribed to the recent work published
by Treub on the occurrence and meaning of hydrocyanic
acid in the tissues of Pangium edule (65), one of the
Bixacese. This compound, according to the author, does
not occur as a glucoside, but in the free condition, and is
present in relatively large amount. Greshoff found more
than 1 per cent, to be hydrocyanic acid of the dry weight
of the plant in one sample among many others analysed.
A brief resumi, of the author's conclusions seems not to be
out of place here, as throwing light upon the question of
the nutritive value of the glucoside of the laurel. Indeed
it seems not improbable that the hydrocyanic acid itself may
be regarded as, in some cases at least, a reserve material.

Treub has made a careful investigation into the
localisation of this principle in the plant, using as his
method the reaction given in the formation of Prussian
blue when hydrocyanic acid comes in contact with a ferric
salt in the presence of hydrochloric acid. The reaction is
very distinct and takes place well in the interior of the
cells, causing those which contain the hydrocyanic acid
to stand out with great distinctness.

In the whole of the adult axis, both stem, root and
peduncles, he finds it to exist in quantity in the conducting
tissue of the bast and pericycle. In the leaves it is still in the
same regions, but is more widely spread, nearly all the
parenchymatous tissue of the blade containing more or less
of it. The epidermis especially is noteworthy, showing it
present in the basal cells of the hairs which the leaves bear,
and in certain idioblasts which contain also crystals of
oxalate of lime. In the young fruits and those which are
growing a considerable quantity is present, partly in the
bast and partly in parenchyma outside the conducting tissue.
In the seeds there is an accumulation in the peripheral
layers of the endosperm and in other cells of the same
tissue abutting on the embryo.

In these regions, and in the cortex, and sometimes the
pith of the axis, Treub describes the hydrocyanic acid as

64 SCIENCE PROGRESS.

existing in special cells which are sharply marked off from
the others round them when stained as above described.
These special cells vary a good deal in number, apparently
according to the amount of the acid present in the plant,
and have no very specially regular distribution. Indeed it
seems probable that any cell of the tissue may become a
centre of deposition of the acid. Generally, if not quite
isolated, they only occur two or three together. Certain of
the fibres of the pericycle may be observed almost similarly
isolated.

Treub further says that these special cells of the cortex
or of the pith derive their supply of hydrocyanic acid from the
conducting tissue of the bast and that the amount of them
and consequently of the acid varies with the condition of
the stem.

Tracing the hydrocyanic acid upwards through the axis
by means of longitudinal sections it can be found to extend
throughout its whole length, but to disappear at a little dis-
tance from the growing point, the apical meristem of which
contains none.

It is impossible to avoid being struck with the similarity
here exhibited to the fate of sugar, amides, etc., which as
we have seen can be traced up to the seats of constructive
metabolism and there cease, apparently giving rise to
protoplasm. If this be so, the hydrocyanic acid must be
regarded as a plastic material, unsuitable as at first sight it
would appear for that purpose.

This view is supported by several observations which
the author details at some length. He finds that in the
apices of young shoots which have suffered an arrest of
growth, there are more of the special cells containing the
hydrocyanic acid than there are in similar ones which are
undergoing rapid elongation. That is, where there is active
consumption of plastic material there is no accumulation of
the acid, but where plastic substances are compelled to remain
unused, hydrocyanic acid is one of such stored bodies.

Another series of observations considerably strengthens
this view, while it points more definitely to the ultimate
purpose of the acid. In many of the special cells the latter

THE RESERVE MATERIALS OF PLANTS. 65

may be seen to be accompanied by quantities of proteid
substance. Taking young cells near the apex of the shoot
the special cells contain the hydrocyanic acid alone, showing
that it precedes proteid in the time of its occurrence. A
little farther back the proteid can be detected, and gradually
as sections are taken at increasing distances from the apex
it increases in amount while the acid diminishes. As the
active life of the cells becomes less and less vigorous, the
proteid becomes more and more preponderating in the cell
contents, and ultimately cells are found which contain
proteid only, the hydrocyanic acid having all disappeared.
The same succession of events can be seen if the develop-
ment of the pericyclic fibres be traced towards the apex of
the stem.

There seems from these observations to be very strong
reasons for supposing that hydrocyanic acid is a nutritive
substance and leads at any rate in these plants to the
formation of proteid.

Treub holds that this is its immediate function ; he
believes it to be primarily formed in the leaves, principally
in the basal cells of the hairs and the idioblasts with calcic
oxalate in the epidermis of the leaves. Thence it makes
its way to the conducting tissues of the bast and pericycle
and travels to the apical meristems. It is thus primarily a
body originating only in the constructive processes, and not,
as in the cases of the almond and cherry laurel, the product
of a decomposition of a glucoside. Indeed Treub says very
emphatically : " L'acide cyanhydrique du Pangium edule
n'est pas un produit de decomposition ou de desassimila-
tion," basing the statement on both indirect and direct
arguments. The former are founded on the localisation of
the product in the bast and pericycle and its evident trans-
portation by the bast tissue. The latter involve the
consideration of its localisation with a material which
serves as a temporary proteid reserve in the same elements
of the tissues, and the order of appearance and disappear-
ance of the two substances in such special cells.

That hydrocyanic acid can subserve not only the for-
mation of temporary reserves of proteid but can be used,

5

66 SCIENCE PROGRESS.

immediately after its first formation, by the leaves in which
it is formed also appears certain. When plants whose
leaves contain it are put for some days in the dark the acid
gradually disappears, and as usual in such cases their whole
metabolism suffers. On being again illuminated the vital
processes gradually resume their activity. If a plant be
put in the dark till nearly all the acid has gone from
the leaves and then it be brought into the light, the little
that remains is soon removed by the returning activity of
the metabolism.

That the acid is used, and not simply transported from
the leaves, can be shown in another way, by cutting a
circular section through the conducting tissue of the petioles,
when removal by transport becomes impossible. Yet the
hydrocyanic acid disappears gradually.

It was said above that in some cases the hydrocyanic
acid itself might be looked upon as a reserve material.
This seems to be the case in the special cells described by
Treub in the cortex of plants when they do not contain
also proteid. In such cases we seem to have temporary
reservoirs to supply local and transitory needs and to
supplement the current passing along the bast. " Dans
les endroits non on pas suffisamment desservir pour le
systeme conducteur liberien ces usines locales prennent
naissance, et en plus grand nombre, a mesure que la
plante a on aura besoin dans ces endroits de plus de
substances plastiques." Thus in the older part of the
stem, where the active life is confined almost altogether
to the cortex, the latter contains many of these special cells,
while they are absent from the rest of the fundamental
tissue. Where they are present, as in certain portions of
the petioles, active life continues, although it may be de-
cadent in other parts.

This temporary storage comes out very prominently in
the cases of the developing fruit and seed. At the base of
the former, just above its point of junction with the pedicel,
there is a very marked accumulation of the hydrocyanic acid,
the cells staining blue under the treatment described being
much more numerous than lower down the stalk. The

THE RESERVE MATERIALS OF PLANTS. 67

peripheral layer of the seed in its young condition is
also supplied very fully with these local reservoirs. We
appear to have here a deposit laid down to supplement the
regular stream which is passing all about the plant by means
of the conducting tissue of the bast. It is doubtless derived
from the circulating supply, for if the latter be interrupted
by a section passing across the stem through its path, the
disappearance of the acid takes place from the bast tissues
below the wound some time before it does from the isolated
special cells of the cortex.

From the work of Treub and of Guignard then it seems
increasingly probable that the glucosides are reserve
materials, and not simply bye-products or products of
excretion. Nor is it apparently only the sugar in them
which has a nutritive value, but the other products of their
decomposition have a particular part to play in the meta-
bolism. This is certainly the case with hydrocyanic acid,
and no doubt further investigation will show that it is the
same with other products similarly formed.

Guignard (66, 67) has made similar researches to those
already described upon the plants of the natural orders
Cruciferae, Capparidaceae, Tropceolacese, Limnanthaceae,
Resedaceae and Papayaceae ; which all contain the ferment
myrosin, a body capable of decomposing more than one
glucoside. There are several of the latter compounds
found in this group of plants, the best known of which are
sinio-rine, ancj sinalbine. Siniorine is found in the black
mustard (Brassica nigra), and is often called myronate of
potassium. On decomposition it yields besides sugar a vola-
tile body, sulphocyanate of Allyl, and potassic hydrogen
sulphate. Sinalbine, as its name implies, is found in the
white mustard (Sinapis or Brassica alba). When decom-
posed the volatile constituent is found to be sulphocyanate
of orthoxybenzyl. Others, the composition of which is not
yet fully known, are those of the watercress {Nasturtium
officinale) which yields phenyl propionic nitrile, the common
cress {Lepidium sativum) affording the nitrile of alpha-
toluic or phenylacetic acid. Though the fate of these
complex volatile bodies has not been investigated, it is

68 SCIENCE PROGRESS.

noteworthy that some of them at any rate contain cyanogen
compounds, which may well be utilised after the manner of
hydrocyanic acid itself as established by Treub.

Their distribution in the plants appears to follow that of
the amygdalin in the Rosaceous group, but very little
definitely is known on this head. The enzyme which splits
them up is according to Guignard always found in special
cells which do not contain the glucoside.

Very closely allied to the group of the glucosides is
that of the tannins, about the importance of which there
has been a good deal of controversy. Some of them are
no doubt glucosides, yielding among their products of de-
composition gallic acid and sugar. Others are apparently
not so associated with a carbohydrate group. They are
very widely distributed, and often occur not only in parts of
plants which are devoted to storage of materials, but in the
tissues where active metabolic work is going on. The
task of deciding whether or no they serve as reserve
materials or as bye-products is consequently not easy.

The two views have been strenuously supported by
different writers. Sachs, while working on the germination
of the Scarlet-runner (68) in which tannin is comparatively
plentiful, suggests an antithesis between carbohydrates
and proteids on the one hand, and the tannins and colour-
ing matters on the other, the latter being in his opinion
only bye-products. He advances in support of his view the
fact that they appear or increase with renewed growth of
the embryo, instead of diminishing as reserve materials
should do. Their appearance is coincident with the chemical
changes in the undoubted reserves which lead to the
utilisation of the latter. The same view is advanced by
Schell (69), who suggests that in some cases, however, it
may be a nutritive product. In the germination of certain
oily seeds, chiefly of plants belonging to the Boroginaceae,
tannin, which is present in addition to the oil, diminishes
in quantity during the germination. In the stem of the
mature plant there is during the winter a considerable
quantity of tannin which almost vanishes as spring ad-
vances. On the other hand he finds in certain almost parallel
cases that the tannin accumulates instead of diminishing.

THE RESERVE MATERIALS OF PLANTS. 69

The view that these bodies have a nutritive value has
been supported with some emphasis by other writers.
Wigand associated it very closely with the carbohydrates,
and thought it was an essential factor in vegetable meta-
bolism. Wiesner also supported the view of its carbohy-
drate relationships, and indicated a probability that it stands
between the starch and cellulose groups and the great class
of resins, etc. The latter relationship has been again
brought forward by Hillhouse (70), who found in Pinus
sylvestris that as resin increases in the stem tannin dimin-
ishes in like proportion, and that the cells surrounding the
resin ducts invariably show its presence. Hartig suggests
that tannin remains in the oak through the winter in the
form of grains similar to starch grains, but distinguishable
from the latter by characteristic reactions. These grains,
he says, are dissolved and utilised in the spring. In his
later writings Sachs inclines to the same view ; he says
that besides those which must be looked upon as excreta or
bye-products, some of the tannins of the oak are most likely
to be regarded as reserve products, on account of their origin
and disappearance and their behaviour generally during the
growth of the plant (71).

The localisation of tannin in the different parts of the
plant does not give us much assistance in determining which
of these views has most to support it. It is often found in
special sacs in the midst of metabolic tissues ; it is very
frequently found in epidermal cells, either in the interior or
saturating the cell wall ; it is extremely prominent in bark.
These positions certainly suggest that it is of but little value
as a food-stuff; on the other hand it is often abundant in
assimilating parenchyma in which starch formation is pro-
ceeding.

In Hillhouse's paper (70) already alluded to, the author
describes a considerable number of observations he made to
determine whether or no a disappearance or diminution of
tannin could be detected in the spring, and if so, whether it
was a reasonable conclusion that such diminution indicated
a utilisation of the vanished portion.

He investigated a large number of trees in which tannin

70 SCIENCE PROGRESS.

is present in greater or less amount, and noted the changes
in the amount present in winter and in spring in their various
tissues. He concludes that in no case is there noticeable a
diminution of tannin in early winter as starch accumulates,
and there is no sign that the starch is formed at the expense
of the tannin. When growth recommences in the spring,
instead of tannin disappearing from the older tissues it makes
its appearance in quantity depending on the amount of
growth. The tissues of the bud are commonly crowded
with it. Hillhouse's experiments proceeded upon three
lines. In the first place plants or parts of plants rich in
tannin were made to grow under conditions in which assim-
ilation of C02 was impossible ; a second set of experi-
ments consisted of germinating in darkness seeds containing
tannin ; and finally corms were investigated to see whether,
as their nutritive material was transported to the newly-
formed corm springing from them, tannin was transferred
together with the starch.

In no case was any diminution or transference found,
except in the case of Pinus sylvestris already alluded to,
when the probability of the tannin being an antecedent of
the resin became evident.

Those tannins which are undoubtedly glucosides must,
however, be of some nutritive value, as they give off sugar
on decomposition taking place. There is some evidence to
show that during the ripening of certain fruits part of the
sweetness is derived from an astringent principle resembling
and probably identical with tannin, which diminishes in quan-
tity as the fruit matures (72).

A similar uncertainty as to its physiological meaning
must for the present be associated with phloroglucin and
the compounds into which it enters, which are to be re-
garded as ethers corresponding to glucosides. There are
two classes of these compounds, which have been described
as phoroglucides and phloroglucosides respectively. The
former include such bodies as hespentine, phloretine, etc.,
while the latter, which contain a sugar group in their for-
mula, embrace aurantine, rhamnine, hesperidine, etc. They
are somewhat difficult to localise, as the reactions they give

THE RESERVE MATERIALS OF PLANTS. 71

are either not well ascertained or not particularly distinctive.
The most reliable is perhaps that with vanilin in the pre-
sence of hydrochloric acid. When this is made to react
upon a cell which contains phloroglucin in the sap, the
latter forms a fine precipitate of red granules which are
composed of a compound of vanilin and phloroglucin, known
as phloroglucivanilni.

Phloroglucin appears to be often present in the plasma
of meristem cells rather than in the vacuole, for when chlo-
ride of vanilin is added to a tissue containing it the colouring
mainly affects the protoplasm, some of the vacuoles remaining
altosfether uncoloured.

The distribution of phloroglucin, like that of tannin,
leaves a good deal of uncertainty as to its physiological
meaning. It has been investigated in recent years by
Waage (73), who has carefully examined representative
plants taken from almost all sections of the vegetable
kingdom. Out of 185 plants submitted to experiment
135 showed it to be present, but in very different quan-
tities. Of the 135, 51 contained a very considerable
quantity, 41 less but still a tolerably large amount,
while in 43 though present only a feeble reaction could
be obtained. Its distribution was to a certain extent
regular, for the author states that if one species contains
it, it is found with tolerable certainty in all the species of
that genus. The plants of the Polypetalae as a rule show
most, while the Gamopetalae and the Monocotyledons are
on the whole poor in it ; lower down in the scale the Vas-
cular Cryptogams and the Gymnosperms are charged with
it to a degree intermediate between the other groups.

Examining the tissues of such plants as contain a con-
siderable quantity it may be found in meristems and in
permanent tissues. In axial organs it occurs in the
epidermis and later in the bark ; also in the parenchyma
of the cortex, and in the sclerenchyma of the tissues more
deeply seated. It is found sometimes in the endodermis ;
also in the dead cell walls of the xylem parenchyma, fibres,
and vessels. The medullary rays frequently contain a
certain quantity. It is uniformly absent from the bast

72 SCIENCE PROGRESS.

fibres and the sieve tubes, and may be present or not in
the pith. When the epidermis contains it, it is usually
in the hairs if any are present ; even root-hairs giving
evidence of a certain amount. Taking the members of the
axis, Waage found that roots as a rule contain more than
stems, unless the latter be rhizomes, in which it is fairly
abundant. Petioles and the peduncles of flowers contain
less than branches. In plants where the axis is highly
charged with it, there is generally a quantity also recog-
nisable in the leaves, chiefly occurring there at the edges
near the endings of the veins, and further in the neighbour-
hood of the vessels of the latter. The palisade tissue of
the leaf has usually more than the spongy mesophyll, and
the upper has more than the lower epidermis. The seed
as a rule contains but little, and that is only in the integu-
ments.

If the disposition may be taken as any indication of
its being a reserve material at all, the probability is that its
value in the latter sense is but slight. The disposition of
varying amounts in the medullary rays and its frequent
presence in the cells of the cambium layer point possibly
to its supplying nutritive material for the latter. On the
other hand, its consistent absence from all parts of the seed
except the integuments seems to indicate that storage of
nutriment is not its main purpose. It may be that its value
to the meristem tissues is based upon its easily oxidisable
character, affording energy thereby, rather than being a
reserve substance. Its occurrence in the leaves in the
localities named suggests a formation in the mesophyll and
a subsequent transport to the axial regions. But against
the view of its value in metabolism as a reserve material
we have the statement that light does not affect its forma-
tion. It is in Waage's opinion found in the cell-sap as a
general rule, rather than in either protoplasm or choro-
plastids. It seems on the whole to be a product of
destructive metabolism, for it occurs in the same cells as
starch and sugar and may be derived from the latter by
abstraction of three molecules of water, C6HI206 - 3 H20 =
C6H6Q3. It seems to resemble tannin in that it often

THE RESERVE MATERIALS OF PLANTS. 73

increases with the greater development of the plant, and in
being frequently plentiful in parts that are thrown off from
the latter, such as old leaves, the coats of fruits, seeds, etc.,
and in regions withdrawn from active metabolism, such as
bark and to a less degree epidermis. In a further paper
Waage and Nickel suggest that it may possibly be a source
of tannin, as the latter is generally found in the same
parts as phloroglucin (74). Tannin does not appear, how-
ever, to give rise to phloroglucin.

Like tannin, therefore, phloroglucin appears to be on the
whole an accessory product and only rarely to act as a
reserve material. The compounds of it which contain
sugar, i.e., the phloroglucosides, may serve as such, yielding
sugar on their decomposition.

In certain cases the alkaloids appear to serve as reserve
materials, though their value in this direction is probably
but slight. Many seeds which contain them in some con-
siderable quantity lose them during germination, and other
bodies, principally amides, replace them in the developing
embryo or young seedling. This is especially the case with
the seed of Lathyrus Sativus, an Indian species which
contains sometimes as much as '5 per cent, of its dry
weight of an alkaloidal product known as viciine (75).

The possibility of alkaloids helping in such cases to
form albuminoid materials or proteids has been pointed out
by Jorissen (76) in his discussion of the chemical processes
incident to germination, in which he claims for them a
certain value as reserve materials. Heckel [jj) comes to
the same conclusion. He carried out experiments with
Sterculia acuminata, Strychnos Nux-vomica, Physostigma
venenostim, and Datura Stramonium, and found in all these
cases that during germination the greater part of their
alkaloidal principles disappears. He claims that this
disappearance is due to a transformation into assimilable
substances under the influence of the embryo. If the
latter be extracted from the seeds, and they be then sur-
rounded by or buried in moist earth, the alkaloids remain
for a considerable time unchanged.

The conclusions of Jorissen and Heckel are disputed by

74 SCIENCE PROGRESS.

Clautriau (78), who finds another explanation of the dis-
appearance of the alkaloids during germination in a possible
destruction of them as deleterious bodies which would
affect prejudicially the development of the young seedling.
He has ascertained with considerable precision the dis-
tribution of the alkaloid in the seeds of Atropa Beliadona,
Datura Stramonium, and Hyoscyamus Niger, and states
that it is confined entirely to a layer of cells situated
between the albumen and the integument of the seed, which
when the latter is mature is very much reduced in its
dimensions. This layer is much more prominent while the
seed is ripening, consisting of many cells with very rich
contents, the latter consisting of starch and albuminoid sub-
stances as well as alkaloids. As the albumen grows, this
nourishing layer gradually yields up both starch and pro-
teids, while the alkaloid persists ; the cells become
gradually nearly empty, and dry up considerably, ultimately
becoming dead. In this condition they still contain the
alkaloid, the quantity of which does not diminish during the
changes described. When the seed is mature, this layer
is very thin, the cells being flattened and compressed to-
gether, forming a sort of membrane in which the alkaloids
remain, partially or wholly combined with an organic acid.

The nutritive value of the alkaloid seems improbable
when we consider the disappearance from this layer of the
starch and proteids, and the retention of the former. If it
were then a reserve product it would in all probability ac-
company the other undoubted nutritive bodies. Clautriau
has obtained further information on this point by depriving
seeds of Datura Stramonium of this alkaloidal layer and
submitting them to germination, either in moist earth or in
an atmosphere saturated with watery vapour. He found
that under such conditions they germinated normally, and
produced young seedlings which differed in no particulars
from normal seedlings of Datura.

Clautriau extended his researches to other plants than
those named, particularly Conium maculatum, from which
he obtained the same results.

Examining the young seedlings grown under these

THE RESERVE MATERIALS OF PLANTS. 75

conditions, no alkaloid being allowed to remain in the seed,
Clautriau found that the active principle made its appear-
ance in considerable quantity, and chiefly in thegrowingapices.
The same thing was noticeable in the development of mor-
phine in the poppy (79), where a more gradual formation
was detected. Morphine does not show itself at the out-
set of the development of the plant, but appears to be
preceded by another alkaloid, giving very clear reactions,
which does not seem to be identical with any of the nitro-
genous principles extracted from opium.

The conclusion that must be drawn from these investiga-
tions is that these alkaloids, and hence probably all such bodies,
are not to be regarded as reserve materials, but as bye-
products or excreta, appearing coincidently with the active
metabolic processes of the growing plant.

Besides these accumulations of more or less complex
organic compounds in the tissues of plants we meet with
certain cases where inorganic material is deposited with a
view to subsequent utilisation. These are, however, of
much less importance and only occur in comparatively few
plants. We have the well-known globoids in the aleurone
grains of the castor-oil seeds, the seeds of Bertholletia
excelsa and several others. From their disposition and
fate, and from the fact that they afford a supply of phos-
phorus, it is probable that we may include them in this
group. In certain cases also the collections of crystals of
calcium oxalate gradually disappear from the cells in which
they are deposited, and so seem to minister to the needs of
the plant for calcium, an element whose function, however,
is still practically unknown.

BIBLIOGRAPHY.

(60) Thome. Ueber das Verkommen des Amygdalins und des

Emulsins in den bittern Mandeln. Botanische Zeitung, p.
240, 1865.

(61) PORTES. Recherches sur les amandes ameres. Journal de

pharmacie et de chimie, t. xxvi., p. 410, 1877.

(62) PFEFFER. Pflanzenpkysiologie, t. i., p. 307, 1881.

(63) JOHANSEN. Sur la localisation de l'emulsine dans les aman-

des. Ann. des. Sc. Nat. Bot., 7 ser., t. vi., p. 118, 1887.

76 SCIENCE PROGRESS.

(64) GuiGNARD. Sur la localisation, dans les amandes et le

Laurier-cerise, des principes qui fournissent l'acide cyan-
hydrique. Journal de pharmacie et de chimie, 5 ser., t. xxi.,
pp. 233-289, 1890.

(65) Treub. Sur la localisation, le transport, et le role de l'acide

cyanhydrique dans le Pangium edule Reinw. Ann. du
Jardin Botanique de Buitenzorg, xiii., p. 189, 1895.

(66) GuiGNARD. Recherches sur la localisation des principes

actifs des Cruciferes. Journal de Botanique (March), 1890.

(67) GuiGNARD. Recherches sur la nature et la localisation des

principes actifs chez les Capparidees, Tropeolees, Limnan-
thees, Resedacees, et Papayacees. Journal de Botanique,

1893-

(68) SACHS. Ueber die Keimung von Phaseolus multiflorus.

Sits, der Wien Akad., 1859.

(69) Schell. Physiologische Rolle der Gerbsaure. Bot. Jalires-

berlcht, 1875.

(70) HlLLHOUSE. Some Investigations into the Function of Tannin

in the Vegetable Kingdom. Midland Naturalist, 1887-8.

(71) SACHS. Vorlesungen iiber PJlanzenphysiologie, 1882.

(72) BuiGNET. Ann. Chemie Phys., ser. iii., Bd. 61, 1861.

(73) Waage. Ueber das Vorkommen und die Rolle des Phloro-

glucins in der Pflanze. Ber. d. dent. bot. Gesell., November,
1890.

(74) Waage and NICKEL. Zur Physiologie des Geitstoffs und der

Trioxybenzol. Bot. Central., 1891.

(75) RlTTHAUSEN. Journ. Jur pract. Chem., new series, vol. xxiv.,

p. 202, 1 88 1.
(j6) JORISSEN. Les phenomenes chimiques de la germination.
Memoires couronncs de I' Acad. Royale de Belgique, lxxxviii.,

P- 73-

(77) HECKEL. Sur l'utilisation et les transformations de quelques

alcaloi'des dans la graine pendant la germination. Comptes
Rendus, January, 1891.

(78) Clautriau. Localisation et signification des alcaloides dans

quelques graines. Ann. de la Societe beige de Microscopie
{Memoires), t. xviii., 1894.

(79) CLAUTRIAU. Recherches microchimiques sur la localisation

des alcaloi'des dans le Papaver somniferum. Mem. de la Soc.
beige de Microscopie, t. xii.

J. Reynolds Green.

jj L I » & A R Yj 3u

AFRICAN GRASS FIRES AND THEIR^ m + £V

EFFECTS. N& V >^

MANY parts of the interior of tropical Africa consist
of wide grassy plains, occasionally varied by
scattered trees, but usually very bare and monotonous in
appearance. In the rainy season these steppes are green
with vigorously growing grass, and patrolled by hundreds
of antelopes and other kinds of game ; a few months after-
wards when the rains are over, they are covered by
blackened ashes and charcoal, and not a living creature will
be visible except perhaps a few birds or a very occasional
ground-rat.

These fires are usually due to the natives, who find
that the bush can be most easily cleared by their assistance,
though they are often lighted to satisfy the childish delight
in a big blaze which is characteristic of the Suahili porter.

Their effects are most interesting, both economically
and also in the way in which they entirely change the
aspect of the vegetation.

It is, of course, immediately obvious that all the valu-
able feeding material of many square miles of luxuriant
grass is by these fires entirely wasted ; but, besides this,
the soil is never permitted to grow rich through the
accumulation of leaf-mould and stems, and in fact the land
is every year brought back into exactly the same condition.
No true turf is formed, and the soil remains more like the
subsoil in cultivated countries and never becomes in the
least improved.

The effect on the vegetation is very curious. The
season of flowering for many trees and herbaceous
plants is completely altered. A large number of low-
growing herbaceous plants possess woody root-stocks or
some sort of underground store of nourishment. With the
very first shower of the rainy season, these stores send up
flowering stems entirely without leaves, and the bare and
blackened earth is studded with the bright purple flowers of

78 SCIENCE PROGRESS.

Dolichos spp., the blue Pentanisia Schweinfurthii, little
white Euphorbias, Lasiosiphon spp., etc. These all have
the appearance of a flower cut off and planted in the earth,
and give rise to remarks on the collector's carelessness in
not bringing leaves when worked up by untravelled
botanists. With the setting in of the rains, the stems
begin to grow and produce leaves until, when the grass has
sprung up, all these herbs are in full foliage. This habit is
of great advantage to the flowers concerned, as insects
can readily perceive the scattered flowers which in the grass
would be quite inconspicuous. The same thing occurs in
many of the trees. Several species of Dombeya, for example,
send out their flowers at this foreshadowing- of the rains
and are most conspicuous.

Another curious effect of the fires is the manner in
which trees are either kept down or obliged to protect
themselves in some way against their action. In the more
arid plains trees seldom exist, or if present occur in the
form of stumps perhaps ten years old, but never able to
grow higher than a foot or so. Such stumps put out every
wet season vigorous shoots, which are annually burnt away
and only the short stem with another layer of wood is left
to survive.

Of the trees which do manage to exist in spite of the
annual conflagration, the most remarkable are the tree
Euphorbias, often twenty to twenty-five feet high. These
have angular fleshy branches protected by a leathery
epidermis, and besides their milky juice, which contains
gum, caoutchouc and other substances, have a large amount
of mucilage or slimy matter in the ordinary tissue. This
latter is a strongly waterholding substance, and the most
violent fire seems unable to do more than scorch a very few
of the outermost branches.

It is a most curious fact that though when living they
resist fires in this wonderful manner, dead branches make
an excellent fire and blaze up most vigorously. I cannot
understand this difference.

Of the other trees which continue to thrive in these
places, there are some seven species which grow in abun-

AFRICAN GRASS FIRES AND THEIR EFFECTS. 79

dance ; there will be usually 500 of one of these species to
every individual of some other kind. I brought home
specimens of the bark of these six or seven forms, which
were given to Professor Bretland Farmer for examination,
who replied as follows : " I examined your specimens of
bark and they all agree in possessing cells which show a
certain amount of gummy degeneration of the cells in the
bark, together with the presence of a considerable amount
of sclerotic cells ; it seems not impossible that these two
facts may be connected with the resistance of the plants to
the fires, and I found as a matter of fact that, on comparing
the rate of burning of these barks with that of laburnum,
they were very slowly consumed.

" I should have added that there are repeated periderms,
and intermixed with the cork are the sclerotic cells
already mentioned." Now the artificially produced cork
of commerce shows great similarity in some respects to
the cork of these fireproof trees. The process adopted
both with the birch and the cork oak is to carefully peel off
the cracked superficial layer of bark or " male cork " (this is
known as "demasclage"). After this the layer of cork
increases enormously and may perhaps attain to 17 cm.
in thickness if left untouched : the result is the ordinary
commercial article. I do not think that it is going too far
to say that we have in grass fires a natural " demasclage "
process, for they will certainly destroy the outer more or
less dead tissues.

From the researches of Henslow,1 Tschirch2 and
Volkens 3 on desert plants, it may be considered proved
that cutin, which most modern authorities consider nearly
identical with suberin, is directly increased by dry and arid
conditions, so that this direct effect is probably also of
use in increasing the deposition of corky matter. Both
evils — -the fire and the drought — have, as so often happens,
brought about their own remedy. The sclerotic cells (or stone
cork ?) may doubtfully be set down to the same cause, for

1 Origin of Plant Structures.

2 Angewandte Anatomie and Linnea, 1881.

3 Flora der egypt. arab. IVuste.

80 SCIENCE PROGRESS.

culture experiments (Duchartre and Henslow, loc. cit., p. 57)
show that sclerenchyma may be directly diminished by a
more moist atmosphere.

The occurrence of gum is not so clearly dependent on
the climatic conditions ; its use in these forms is, however,
obvious enough, for all apertures by which water might be
lost are, so to speak, gummed up. This is quite similar in
physiological action to the drops of mucilage or gum which
hermetically seal the vessels exposed by cutting across a
branch of any ordinary deciduous tree.

It is true that the production of gum is known to be
most abundant in a dry and hot season, but according to
the explanation given by Tschirch, loc. cit., p. 2 1 1 (and an
identical account has been given me by Mr. Malcolm Dunn
as the result of experience), this is due to the gum being
squeezed out by the contraction of the bark following on a
wet period, during which the masses of gum in the bark
are greatly swollen. I cannot find any explanation of the
actual cause of the change of cellulose into gum, but Mr.
Malcolm Dunn states the general opinion that it is abundant
after a severe shaking of the trees, as, for example, in a violent
wind. Such places as those here treated of are certainly
exposed to wind (otherwise they would be covered by
forest, according, that is, to my experience), and it is possible
that the wind may have assisted in starting gum formation ;
but if, as is not unlikely, the wind acts indirectly by straining
the layers of the cell walls, it seems more probable that the
fierce heat of the fire, causing sudden and violent shrinking
and warping of the bark, strains the cell walls in the same
manner. This may of course be quite unproved, but the
facts are sufficiently interesting to justify further research.

G. F. Scott Elliot.

Bcimce progress.

No. 26. April, 1896. Vol. V.

THE GENERAL BEARINGS OF MAGNETIC

OBSERVATIONS.

IF necessity be the surest prompter of invention, it is not
too much to say that the necessity of the navigator
has been a most potent factor in producing the observer of
the elements of Terrestrial Magnetism. The traveller on
land might rest during darkness until daylight enabled him
to resume his journey ; but the seaman on the trackless
ocean was dependent upon the indications of his compass
by day and night ; and after the discovery of Columbus
that the magnetic Declination or Variation of the needle
from the direction of the geographical North varied in
amount with the Latitude and Longitude, a new impetus
was given to observation.

The publication of Gilbert's grand discovery that the
earth is a magnet and the director of the freely suspended
needle, followed by the discovery of the secular change in
the value of the Declination, naturally added to the desire
of both landsmen and seamen to know as much as possible
concerning that great magnet, both from purely scientific
reasons and to meet the practical ends of the navigator.
Thus the seventeenth and eighteenth centuries were re-
markable for the number of observers both of the magnetic
Dip and Declination.

So important had a correct knowledge of the Declination

become to the requirements of navigation, as early as the

close of the seventeenth century, that Halley, under the

6

82 SCIENCE PROGRESS.

immediate auspices of the Government, made his celebrated
voyage over the Atlantic Oceans in a man-of-war, in order
that intelligent observation should set at rest much that was
doubtful. The results of this voyage, combined with the
observations of previous navigators, were embodied in his
celebrated chart of lines of equal value of magnetic Varia-
tion or Declination, the first of its kind and of so convenient
a form that charts of equal values of the three magnetic
elements are to this day the most acceptable form for
representing the combined results of magnetic observations
made over large areas of sea and land, as well as of the
special magnetic surveys which in recent years have been
made in various countries.

Here we may pause to consider the word Declination as
applied to the angle which the direction of the horizontal
magnetic needle makes with the true meridian. Many
magneticians object to the word, but no better has yet been
proposed or at any rate accepted ; the result being that
while observers on land use the term, seamen adhere firmly
to the expression "Variation of the Compass". This is as
might be expected when it is remembered that navigators
look upon the word Declination as connected with the posi-
tion of the sun and other heavenly bodies, and would find it
most inconvenient to have the same word in daily use,
meaning two totally different things.

During the eighteenth century charts of the magnetic
Declination were published by Mountaine and Dodson,
Bellin, and Churchman, and for their time may be con-
sidered as fair approximations to the truth. Churchman's
design was not only to give values of the Declination but
to furnish the seaman with a means of ascertaining the
Longitude, an ambitious project, especially as we now
know there were probably considerable elements of error
in these charts caused by local magnetic disturbance of the
observing compass on land, and from the iron used in con-
struction disturbing the compass on board the ships.

This latter source of error was only beginning to be
viewed in its true light at the close of the eighteenth
century.

THE BEARINGS OF MAGNETIC OBSERVATIONS. 83

In the years 1801-2 Commander Flinders of H.M.S.
Investigator, then surveying the southern coasts of Australia,
found that when his vessel's head was north or south by
compass the observed Declination agreed very nearly, but
when she lay with her head east or west, it differed largely.
Moreover these errors on the east and west points of the
compass had the opposite sign to those observed in Eng-
land.

Flinders, however, had supplemented the existing
scanty knowledge of the distribution of the Dip over
navigable waters by several observations of his own in
northern and southern latitudes, and from these he drew
the conclusion that the errors in the Declination observed
on board ship were caused by magnetism induced by the
earth in the vertical iron of the ship, and changed in value
proportionally to change of Dip. Here Flinders was wrong,
as the errors were really proportional to the tangent of the
Dip.

In spite of this mistake he was enabled from his know-
ledge of the Dip to conceive the idea of so placing vertical
bars of iron that they produced an equal and opposite effect
on the compass to that of the ship in all latitudes, and thus
invented what is now called the Flinders bar, one of the
most important correctors of compass disturbance in the
iron and steel ships of the present day.

In 1 8 14 Flinders induced the Admiralty to have ex-
periments made on board men-of-war at Portsmouth,
Sheerness, and Devonport, to ascertain the amount of the
magnetic disturbance of the compass caused by the iron in
each ship. The chief reason for making these experiments
was to show the necessity for ascertaining and applying
these errors to ensure the safe navigation of the ships, but
it had also a direct bearing in enabling observers to elimi-
nate the hitherto inexplicable divergencies in the values of
the Declination observed in different ships in the same
geographical position. The results of these experiments
bore no immediate fruit, for with the death of Flinders the
subject was temporarily neglected.

In 1 8 19, Hansteen published his Magnetismus der Erde

84 SCIENCE PROGRESS.

with an atlas containing charts of the elements Declination
and Dip for different epochs between the years 1600 and
1787. These charts were in a large measure compiled from
observations made with imperfect instruments and subject
to the causes of error already mentioned attending both land
and sea results. Hansteen, however, considered them of
sufficient value to enable him to draw certain important con-
clusions with regard to the cause of the secular change of
the magnetic elements. Thus he not only concurred with
Halley that the earth considered as a magnet had four
poles or points of attraction, but computed their geo-
graphical positions. Further than this, he computed that
to account for the secular change these four supposed
poles revolved round the terrestrial poles, each pole
occupying a widely different number of years to complete
the revolution.

If these theoretical results had been true, a great
advance would have been made not only in the science
of terrestrial magnetism but in its practical bearing on the
requirements of the present day.

Although Humboldt had about the year 1800 shown
that the intensity of the earth's magnetism varied with the
latitude, the general distribution of that magnetic element
was so little known that we may with our present extended
knowledge consider that Hansteen's conclusions were based
on insufficient data. In fact the idea of the earth being a
magnet with four poles has long since been abandoned in
favour of there being one pole with two foci of intensity in
each hemisphere, and reasons will be given further on
which tend to throw doubt on there being any revolution of
these two magnetic poles round their adjacent terrestrial
poles.

Subsequently to Hansteen's charts there appeared those
of the Declination by Yeates, Duperrey, and by Barlow in
1836. These were useful to navigation but helped very
little towards the solution of the problem of the ever vari-
able distribution of the earth's magnetism.

Besides this by the year 1835 the iron-built ship had
appeared on the ocean and a correct knowledge of the

THE BEARINGS OF MAGNETIC OBSERVATIONS. 85

three magnetic elements became a necessity in solving the
problems which the magnetism of different iron ships
presented.

With Gauss's invention of the absolute horizontal force
magnetometer in 1833, many hitherto unknown move-
ments of the magnetic needle of the highest interest were
discovered, which with the coarser instruments previously
in use lay concealed. This discovery gave the desired
impetus to the scientific men of that epoch, and the period
included in the years 1835-45 was "a time of unparalleled
activity in the extension of systematic and accurate mag-
netical observations over the earth's surface ".

Whilst most of the continental nations joined in this
movement, the principal share in the work was divided
between Germany, Russia, and England in Europe, and the
United States in America. But before the splendid series
of simultaneous observations made on the continent, and
four British colonial observatories were organised, Gauss
in 1839 published his general theory of Terrestrial Magnetism
coupled with a series of charts of the three magnetic elements
for the whole world, based upon observations made at
ninety-two selected stations distributed over the earth's
surface ; and it may be remarked that Gauss's charts not
only gave results in fair accordance with observation in
explored regions, but also as afterwards proved in Antarctic
latitudes hitherto unvisited by man.

The proof came in the years 1839-43, when Ross's
Antarctic voyage of exploration was carried out in the
interests of terrestrial magnetism. Besides the importance
of a knowledge of the general distribution of the magnetic
elements in those regions, one great aim of this expedition
was to reach the south magnetic pole. This was found to
be impossible, but sufficient data were collected to give its
approximate position. Whilst this Antarctic magnetic
survey was being completed, that of British North
America was also undertaken with the result of the deter-
mination of the locality of one of the foci of greatest
intensity in the northern hemisphere.

The results of these surveys formed, as will be well

86 SCIENCE PROGRESS.

remembered, a valuable series of "contributions" to terres-
trial magnetism by Sabine, and, coupled with every available
observation between the years 1818 to 1876, formed the
materials for the series of charts entitled " The Magnetic
Survey of the Globe " for the epoch 1842*5. Each map
gave normal lines of equal values of the Declination, In-
clination and Intensity. Although it may be said that from
the Arctic circle to the Antarctic, the direction of the lines
was efficiently given by observation, the lines within those
circles were largely taken from Gauss's computed lines
modified to agree with observation.

Another difficulty in compiling these charts of Sabine's
with accuracy lay in the uncertain knowledge of the secular
change then available, and which had to be applied to
observations made so far apart in time.

Sabine's charts are doubtless the best we have for the
epoch 1842*5, but in the light of the requirements of
modern science they leave much to be desired as regards
the Antarctic regions. The observations south of 6o° S.
were made entirely on board ships, where the errors of the
compass sometimes exceeded 50° due to the horizontal
forces in the ship, thus rendering accurate observations of
the Declination very uncertain and correction of the observed
Inclination very difficult ; besides which there are no
records of the ship's disturbing force in the vertical direc-
tion.

Naval requirements, however, did not permit of any
delay in publishing magnetic charts affecting navigation,
for in 1846 the Hydrographer of the Admiralty requested
Sabine to provide charts of the Declination for the Atlantic
Oceans from 6o° N. to 6o° S. These were largely used until
Evans's chart of the Declination for the whole navigable
world was issued in 1858.

The excellent work of Flinders already referred to, of
ascertaining from his knowledge of terrestrial magnetism
the chief cause of the deviation of the compass in wood-
built ships, and providing a corrector for those deviations,
had to be followed up on a much larger scale and with
more exact methods in the iron-built ship, which, in that

THE BEARINGS OF MAGNETIC OBSERVATIONS. 87

period of activity in terrestrial magnetic science — 1835-45 —
was rapidly increasing in numbers on the ocean.

Thus in 1835 observations were made on board iron
ships showing that they acted as a magnet on their com-
passes, but there was nothing to show in the results what
the causes of this condition of the iron ship were, until
Poisson in 1838 published his celebrated "Memoir on the
deviations of the compass produced by the iron in a ship ".
This was a rigorous mathematical investigation of the
subject, showing that the deviations of the compass were
due to induction in the ship by the magnetic force of the
earth.

If the iron ship had simply been built for service in one
locality, a limited knowledge of terrestrial magnetism would
have sufficed to elucidate the causes of her magnetic con-
dition ; but she was destined to traverse every navigable
sea over large changes of magnetic latitude, hence the
necessity for an accurate knowledge of the distribution of
magnetism over the great parent magnet, in order to
determine the magnetic condition of her comparatively
minute offspring the magnetised iron ship ; and this at all
times and in all places in the interests of navigation.
Observations of the terrestrial magnetic elements were
therefore an absolute necessity if iron-built ships were to be
substituted for those of wood.

The ability to predict the deviation of the compass on
change of latitude did not, however, satisfy Airy, for after
a remarkable mathematical investigation of iron ship's
magnetism of a less rigorous character than Poisson's, but
sufficiently accurate for his purpose, he in 1839 proposed
his methods of annulling the deviation of a ship's compass
by means of magnets and soft iron, so arranged as to pro-
duce equal and opposite magnetic effects to that of the
ship. Provided with Airy's admirable and simple directions
this method of correction was comparatively easy in one
latitude, but experience at sea, especially in voyages to the
Cape of Good Hope, showed that every iron ship required
a different application of Airy's correctors.

To discriminate between the amount that was to be

88 SCIENCE PROGRESS.

corrected by permanent magnets, by horizontal soft iron,
and by vertical soft iron, an accurate knowledge of the
magnetic elements Dip and Intensity obtained from obser-
vations on land and at sea was essential.

Before dismissing the subject of the above application
of magnetic observations, it may be remarked that we have
now heavily armed, protected steel cruisers steaming over all
parts of the world with less change of deviation of the
compass than the wood-built Erebus and Terror of Ross's
Antarctic expedition, and this remarkable result could not
have been achieved if the terrestrial magnetic observer had
not done his work.

Moreover, if magnetic observations are not continued
the secular change of the magnetic elements will soon
commence to mar the precision with which our rapidly
moving ships traverse the globe.

The voyage of the Challenger in 1872-76 contributed
the most valuable series of observations of the magnetic
elements in modern times, when the large areas of the
principal oceans traversed by that vessel during three and
a half years are taken into consideration. These observa-
tions, combined with those taken from every available
source, both British and foreign, between the years 1865-87,
formed the materials from which the magnetic charts of
1880 were compiled (see vol. ii., Physics and Chemistry,
part vi., Voyage of H.MS. "Challenger").

The Challenger only crossed the Antarctic circle at one
point in longitude 78° EM and, therefore, although we know
large secular changes to be going on south of 400 S. we have
no measure of the amount, nor anything like an accurate
knowledge of distribution of the earth's magnetism in those
regions. This points to the necessity for a new Antarctic
expedition.

In the year 1888 the late Professor J. C. Adams was
provided with a complete set of magnetic charts for the two
epochs 1842-5 and 1880 previously mentioned, and as it
was known he had directed his profound mathematical
ability to the analysis of the results contained in them, it
was hoped that some new and important light might be

THE BEARINGS OF MAGNETIC OBSERVATIONS. 89

thrown upon the bare facts presented. His lamented death
occurred without his publishing any results.

If, however, reference be made to the report on the
magnetical results of the Challenger, a discussion of the
secular change is contributed founded in a great measure
on a comparison of those charts. The outcome of this
discussion is to throw considerable doubt upon the theory
that the motion of the magnetic poles round the terrestrial
is the cause of secular change ; in fact, that the magnetic
poles remain fast, and we must look elsewhere for the cause
whatever it may be.

Magnetic observations have so far been considered in
their all-important bearing as necessary to safe navigation
in wood-built ships, and in a far higher sense as indispens-
able to that of the iron- or steel -built ships which now
cover the ocean ; the magnetic charts hitherto generally re-
quired for these purposes being those on which normal
lines of equal values have been given, but something more
is now needed.

Observation in comparatively recent years has shown
that not only are there large " regional " magnetic dis-
turbances extending over large areas of land, but that in
moderate depths of water where the largest ship can navi-
gate freely, the land below is also found to have considerable
areas of local magnetic disturbance which, if not allowed for,
may in thick or foggy weather lead ships into danger by
seriously disturbing their compasses.

The United States have done excellent work in pro-
ducing charts of iso-magnetic lines, or charts in which the
chief local magnetic disturbances are recognised, and the
full results of observation recorded. The maonetic sur-
veys of Riicker and Thorpe in the British Isles, of Moureau
in France, of Rijckevorsel in Holland and elsewhere, have
thrown considerable light on the magnetic conditions of
those countries, but there remain whole continents to be
covered by the observer.

The direction of the iso-magnetics too from the deep
sea to the dry land of the coasts is an extension of the
subject, which the observer has hardly touched as yet, but

go SCIENCE PROGRESS.

one affecting the safety of navigation, as well as the question
that has been raised, whether the water areas of the globe
are as a whole more, or less magnetised than the land areas.

To possess charts of iso-magnetic lines for even a few
countries is an evidence of considerable advance in the
knowledge of terrestrial magnetism, for if reference be
made to Sabine's lines of intensity in his contribution on
the magnetic survey of North-West America it will be
found that he rejected certain observations he considered
abnormal and defective, which Lefroy the observer con-
sidered to be his best and naturally retained in his map ;
the result being a considerable difference in the form of the
curves adopted by the two magneticians, Sabine giving
normal curves, Lefroy iso-magnetics.

Respecting the local disturbances of the needle which
have been so clearly proved, the question naturally arises,
whence the cause of these disturbances ? It is now believed
by many, if not finally accepted, that Rlicker and Thorpe
have answered the question by the results of their laborious
survey of the British Isles, coupled with Riicker's elegant
investigations as to the permeability of specimens of the
rocks taken from the localities in which magnetic dis-
turbances were found. Their answer is to the effect that
these disturbances, which have been found to extend over
a region 230 miles long by about 110 miles broad, are
due to induction by the earth's magnetism in rocks of dif-
ferent permeability, either present as in the basalts on the
surface or concealed by superficial deposits.

These results are distinct from the extraordinary dis-
turbances of the needle when in the immediate vicinity of
permanently magnetised rocks, and when the radius of dis-
turbance may be only as many feet as the extent of the
regional disturbance is in miles.

The points of interest in the question of regional
magnetic disturbance are not confined to the magnetician,
for the geologist cannot afford to neglect the valuable in-
formation the magnetic needle affords. Thus although
Rlicker and Thorpe have since made a second and more
elaborate survey of the British Isles, their remark of 1890

THE BEARINGS OF MAGNETIC OBSERVATIONS. 91

that "the kingdom can be divided into magnetic districts
in which the relations between the direction of the disturb-
ing forces and the main geological characteristics are so
suggestive as to be worthy of careful statement and further
investigation," not only holds good, but has received con-
firmation.

The mining engineer is deeply interested in a know-
ledge of the Declination. Charts of normal lines are of
great use to him whether above or below the earth's surface,
but especially below when he has no other guide. To such
an one a knowledge of regional magnetic disturbance as de-
duced from surface observations is most important, as it
tells him that he is in the neighbourhood of magnetic
rocks, the disturbing effect of which on his compass needle
may be far greater in the depths of his mine and turning it
into a treacherous guide.

We have now considered magnetic observations in a
measure from the point of view of the immediate practical
results which their scientific treatment produces, but who
will say in this great maritime nation that the work of mag-
netic observers, even if solely to make navigation poss'ble,
is not worthy of the fullest consideration ?

There is besides a vast field of inquiry for the observer of
terrestrial magnetism in unravelling thesecretsof the earth con-
sidered as a magnet, and the ceaseless change of its magnetic
condition which the needle tells us of, for which no immediate
practical result can be foreseen, yet is worthy of the attention
of the ablest physicists and most advanced mathematicians.

Inquiry into the causes of the secular change is one
requiring the fullest attention, but observation has not yet
done sufficient work. It certainly has done much in certain
countries, and for a large portion of the world as regards
secular change in the past, and data obtained for predicting
future changes for a few years, but only one expedition has
examined the Antarctic regions magnetically, and it is
doubtful if any substantial progress will be made until a
second expedition is made thither, one profiting by the
experience of its precursor, and equipped with possibilities
for work hardly hoped for by Ross.

92 SCIENCE PROGRESS.

It may be remarked in passing that a remarkable
alteration in the amount of the secular change has been
noticed in the Declination and Inclination at the following
observatories : Bombay, Batavia, and Hong Kong about
the period of the eruption of Krakatoa in 1883. This may
be only a coincidence, but may it not also point to the
possibility that the changes below the surface of the earth
which culminated in that mighty explosion, and may still
be at work, have had, and continue to have, magnetic
effects which are recorded by the needles at those observa-
tories ?

Critical investigations have for many years been directed
to the elucidation of the causes of the observed diurnal
variations of terrestrial magnetism. This work was long
seriously retarded by the various methods adopted at different
observatories for recording their results, obliging those who
entered upon a comparison of such results to go through a
tedious conversion of them into a common method. It may
be said that the first large departure from this objectionable
practice occurred when the International Polar Inquiry of
1882-83 was undertaken by the various expeditions.

This was an important step in the right direction, but
there remains much to be done, as shown by the ten re-
ports of the British Association Committee on "the best
means of comparing and reducing magnetic observations ".
Their last report consists of an able and suggestive paper
by Dr. Chree, being the analysis of the results of five years'
observations on "quiet days" at Kew, and is well worthy
of attention as indicative of the present state of our know-
ledge as regards the diurnal variation of the three magnetic
elements.

Such investigations only encourage one in the hope that
the much required observations in southern latitudes may
be undertaken. The observatories at the Cape and Mel-
bourne could do invaluable work if it were carried out on
the lines of Kew, for example.

Lastly, what more is there to be said about magnetic
observations and their bearings ? We do not know why
the earth is a magnet, the cause of the secular change of its

THE BEARINGS OF MAGNETIC OBSERVATIONS. 93

magnetism, why it is subject to solar diurnal, lunar diurnal,
sidereal diurnal and the other variations and disturbances,
nor the cause of magnetic storms, although we can observe
connections between them, earth currents, and aurorae.
Whether the causes of all these exist below the surface
of, or are external to, the earth, or are a combination of
the two, has still to be learnt, and it seems hardly too much
to hope that the restless needle will sooner or later be the
means of opening up sources of knowledge invaluable to
cosmical science, as well as to those only concerned with the
planet upon which they dwell.

When the causes of the secular change are understood
there will be no difficulty in providing the navigator with
magnetic charts for years in advance, much as the tides can
now be tabulated for his use. In the latter case observa-
tion has done its work for several frequented ports, in the
former case a vast amount remains to be done, and the
word that goes forth is still, as Lord Kelvin thrice said
on a kindred subject connected with ships' magnetism,
" Observe".

Ettrick W. Creak.

THE PRESENT POSITION OF THE CELL-
THEORY.

PART I.

A FEW years ago a discussion of the cell-theory would
have seemed superfluous. To-day, partly because
of criticisms which have been directed against the theory,
partly because of the great increase of our knowledge re-
specting cell-structure, the advantage and even the necessity
of such a discussion will be admitted by everybody who has
read and reflected on the subject. In what follows, I
propose to examine the cell-theory in the light of recent
criticisms and researches. I set out with the intention of
avoiding anything in the shape of polemical writing, but I
fear that I have in places fallen away considerably from the
course which I had proposed. In a much disputed subject
controversv is inevitable, a circumstance which need not be
regretted, for controversy is the whetstone of argument, and
obliges those who engage in it to be doubly careful both of
their facts and of the language in which they express them.
My antagonists will, I hope, give me the credit of the
desire to deal fairly with their arguments and criticisms, and
will acquit me of unnecessary bitterness. It has been my
object to elucidate the subject in hand rather than to try to
gain a dialectical advantage.

It is advisable, before entering on the examination, to
have a clear conception of what the cell-theory really is.
This is the more necessary because one of its most recent
critics, Mr. Adam Sedgwick, has complained than nobody
will define the theory in an exact manner ; it is, he says, a
kind of phantom which takes different forms in different
men's eyes. I have shown in another place that this state-
ment is hardly fair, because there are some authors whose
researches on cytology entitle them to speak with authority
who have recently defined the cell-theory in a very precise
manner, though it may be conceded that there are biologists

THE PRESENT POSITION OF CELL-THEORY. 95

whose views are not so exact, and who habitually commit
themselves to statements which on careful examination may
prove to be altogether untenable.

It was pointed out some time since by Whitman,1 and I
have since emphasised the fact,2 that in his broad generalisa-
tions Schwann defined the cell-theory in a very exact manner,
and that the words originally used by him are perfectly
applicable to the cell-theory as it has been held up to the
present time. In saying this, I do not forget that Schwann
held some very erroneous views as to the nature and
structure of cells, which he regarded as vesicles, filled with
fluid, which made their appearance in a structureless matrix,
named for this reason, a cytoblastema. But Schwann's
work consisted of two parts, a statement of observations,
which have proved to be entirely erroneous, and a theory
of organisation, which has been very fruitful of results. He
was careful to say that his theory was only a provisional
explanation which suited the facts as nearly as possible, and
it is a great merit of the theory that it afforded such an in-
sight into organisation that the essential part of it did not
cease to be serviceable long after the "facts" on which it
was founded were shown to be, for the most part, false.
We need not therefore concern ourselves with the fact that
Schwann's conceptions of the origin and structure of cells
were false, but we may examine his theory and see how
much of it we may hold to, and how much we must reject
at the present day.3

Schwann was a very cautious writer, and the quotations
which are given below will dispose effectually of the state-

1 C. O. Whitman, "On the Inadequacy of the Cell-theory of Develop-
ment, "Journal of Morphology, viii., p. 639, 1893.

2G. C. Bourne, "A Criticism of the Cell-theory," Quart. Jour. Micro-
scopical Science, xxxviii., p. 137, 1895.

3 A large part of Schwann's theory of cells, viz., that part of it which
compared cell-formation to the process of crystallisation, was soon shown
to be untenable. But as this part was based on his erroneous views on
the structure and origin of cells, I have passed it over, since the falsity of
his views on this subject involved the falsity of as much of his theory as
was founded on them.

96 SCIENCE PROGRESS.

ment which stands in the first paragraph of Whitman's
work, that he believed that in cell-formation lies the whole
secret of organic development. There are, says Schwann,
two possible theories on the subject of organic development:
(i) The organism theory, namely, that there is an inherent
power modelling the body in accordance with a predominant
idea. (2) The physical theory, namely, that the funda-
mental powers of organised bodies agree essentially with
those of inorganic nature. Rejecting the former of these
two theories as being outside the domain of physical science,
Schwann went on to write : x " We set out with the sup-
position that an organised body is not produced by a
fundamental power which is guided in its operation by a
definite idea, but is developed according to the blind laws
of necessity by powers which, like those of inorganic
nature, are established by the very existence of matter.
As the elementary materials of organic nature are not dif-
ferent from those of the inorganic kingdom, the source of
the organic phenomena can only reside in another com-
bination of these materials, whether it be in a peculiar
mode of union of the elementary atoms to form atoms of
the second order, or in the arrangement of these con-
glomerate molecules when forming either the separate
morphological elementary parts of organisms, or the entire
organism. We have here to do with the latter question
solely, whether the cause of organic phenomena lies in the
whole organism or in its separate elementary parts. If
this question can be answered a further inquiry still re-
mains as to whether the organism or its separate elementary
parts possess this power through the peculiar mode of
combination of the conglomerate molecules or through the
mode in which the elementary atoms are united into con-
glomerate molecules."

Is it not perfectly clear from this that Schwann fully
recognised that there was a further question underlying

xTh. Schwann, Microscopical Researches into the Accordance in the
Structure and Growth of Animals and Plants. Translated by Henry
Smith. London: Printed for the Sydenham Society, 1847.

THE PRESENT POSITION OF CELL-THEORY. 97

the cell-theory, and do not the words which he used with
regard to the union of elementary atoms to form atoms of
the second order show a prescience of the assumptions
which would have to be made to explain the powers mani-
fested by cells ? Because he confined himself to the one
question, it is not fair to say that Schwann had not a clear
appreciation of the importance of the other. I may relate,
in this connection, an anecdote which will finally clear
Schwann's reputation from the reproach fastened upon it.
Professor Lankester tells me that about the time when a
sort of jubilee was held in Schwann's honour at Liege in
1878, he was introduced to him, and ventured to ask in
the course of conversation how it was that after the publica-
tion of his famous essay he had so long been silent.
Schwann answered that he had not been idle, but that
ever since he had been unsuccessfully occupied in trying to
find out the secret of the constitution of the cell.

To return to the question propounded by Schwann,
does the cause of organic phenomena lie in the organism or
in its separate elementary parts, the cells ? He answers
very decidedly, in the separate elementary parts, and gives
the following reasons for his answer: " All organised
bodies are composed of essentially similar parts, namely, of
cells ; these cells are formed and grow in accordance with
essentially similar laws, and therefore these processes must
in every instance be produced by the same powers. Now
if we find that some of these elementary parts not differing
from the others are capable of separating themselves from
the organism and pursuing an independent growth, we may
thence conclude that each of the other elementary parts —
each cell — is already possessed of the power to take up fresh
molecules and grow, and that therefore each elementary
part possesses a power of its own, an independent life, by
means of which it would be enabled to develop itself in-
dependently if the relations which it bore to external parts
were but similar to those in which it stands in the organism.
The ova of animals afford us examples of such independent
cells apart from the organism."

A little further on he says : " In inferior plants any given

7

98 SCIENCE PROGRESS.

cell may be separated from the plant and can grow alone.
So that here are whole plants consisting of cells which can
be positively proved to have independent vitality. Now as
all cells grow according to the same laws, and consequently
the cause of growth cannot in one case lie in the cell, and
in another in the whole organism, and since it may be
further proved that some cells, which do not differ from the
rest in their mode of growth, are developed independently,
we must ascribe to all cells an independent vitality, that is
such combinations of molecules as occur in any single cell
are capable of setting free the power by which it is enabled
to take up fresh molecules. The cause of nutrition and
growth resides not in the organism itself but in its separate
elementary parts. . . . The manifestation of the power
which resides in the cell depends upon conditions to which
it is subject only when in connection with the whole or-
ganism."

The whole theory is very succinctly summed up in the
following passage : " The elementary parts of all tissues are
formed of cells in an analogous though very diversified
manner, so that it may be asserted that there is one uni-
versal principle of development for the elementary parts of
organisms, however different, and that this principle is the
formation of cells ".

No doubt objection may be taken to-day to the uni-
versality of this statement, but if we modify the last part
of it and read " that the most general principle of develop-
ment for organisms, however different, is the formation of
cells," we shall have very nearly expressed the truth, as we
know it at the present day.

I have found it necessary to quote Schwann's work at
considerable length, and to repeat more emphatically what
I stated in my previous essay on Epigenesis and Evolution.1
Dr. Whitman,2 in a reply which deals partly with my

1 G. C. Bourne, "Epigenesis and Evolution," " Science Progress,"
vol. i., 1894.

2 C O. Whitman, Evolution and Epigenesis. Boston : Ginn & Co.,
1895.

THE PRESENT POSITION OF CELL-THEORY. 99

criticisms, and partly with the much more weighty argu-
ments brought forward at the same time by Dr. Oscar
Hertwig, says that my criticisms, in so far as they are
directed against the inadequacy of the cell-theory of develop-
ment, are largely the result of misunderstanding ; this may
in part be true, but I cannot have misunderstood the simple
meaning of his first paragraph, and I wish to insist on the
fact that the cell-theory, as it was promulgated by Schwann,
did not regard cell-formation as the whole secret of organic
development, and that the cell was not, in the mind of the
author of the cell-theory, the alpha and omega of both
morphological and physiological research in the animal
kingdom. If this is clearly understood at the outset, it will
help to remove much possible misunderstanding.

But, as Mr. Sedgwick has rightly said, we have to deal
not only with what its authors thought, but with the cell-
theory as it is understood and taught at the present day.
I have already pointed out * that the most recent definition
of the cell-theory is, to all intents and purposes, identical
with the broader generalisations of Schwann. Dr. Oscar
Hertwig writes : 2 " Animals and plants, so dissimilar in their
outward appearances, are similar in the essentials of their
anatomical structure, since both are composed of similar
elementary parts which for the most part are only recognis-
able by the microscope. . . . Since the cells, into which
the anatomist resolves vegetable and animal organisms, are
the bearers of the vital processes, they are, as Virchow has
expressed himself, the vital units. Viewed from this stand-
point the whole life process of a composite organism appears
to be nothing else than the extremely complicated result of
the individual life processes of its numerous and variously
functional cells." This is simply a restatement in other
words of two of the fundamental principles of Schwann,
namely (1) that the elementary parts of all tissues are formed

1 G. C. Bourne, "A Criticism of the Cell-theory," Quart. Jour. Micr.
Science, vol. xxxviii., p. 137, 1895.

2 O. Hertwig, Die Zelle utid die Gewebe. Berlin : R. Friedlander
und Sohn, 1893.

ioo SCIENCE PROGRESS.

of cells ; (2) that the cause of nutrition and growth resides
not in the organism but in its separate elementary parts.

The attacks which have recently been directed against
the cell-theory may be resolved into contradictions of these
two fundamental propositions. On the one hand there is
the considerable number of cytologists, whose opinions
may be taken to be summed up in Whitman's essay on
the inadequacy of the cellular theory, who deny the second
proposition, and in so doing implicitly deny the truth of
the first. They would say that the cause of nutrition and
growth does not reside in the cells considered as elementary
parts, but in parts still more elementary, the ultimate vital
units of which the cells themselves are composed. On
the other hand Mr. Adam Sedgwick denies the first pro-
position in toto. He states boldly that the elementary
parts of tissues are not formed of cells, but of a continuous
mass of vacuolated protoplasm containing nuclei.1 These
objections, though they are raised from different stand-
points, are not irreconcilable, but it will be convenient to
deal with them separately. First let us consider the
objections to the cell as an ultimate vital unit.

These objections are of long standing. They were first
brought forward by Briicke 2 in 1861 ;3 not long afterwards

1 Since this was written Mr. Sedgwick has published a further account
of his views, which makes it necessary to modify this statement. See
infra.

2 Ernst Briicke, " Die Elementarorganismen," Sitzungsberichte der K.
Akademie der Wissenschaften, Wien, bd., xliii., p. 381, 1861.

3 Delage points out that the merit of regarding protoplasm as an
organised substance belongs to Dujardin, and not to Brucke. At the
same time he points out the essential difference between Briicke's concept
of organisation and that of Dujardin, greatly to the advantage of the latter :
" La difference entre Dujardin et Brucke est tres simple. Le premier a
devine l'existence de structures que le microscope demontre aujourd'hui ;
tandis qu'en introduisant dans la conception de protoplasma cette notion
acceptee avec enthousiasme, d'organismes tres compliques et invisibles,
Brucke a ouvert la porte aux nombreuses theories speculatives qui cher-
chent a imaginer la structure de ces organismes pour expliquer par elles les
phenomenes de la vie." Delage adopts the expression organisation, saying :
" Le protoplasme n'est pas simplement, comme on l'a cru longtemps, une
substance chimique organique, mais il est organise, c'est-a-dire possede une

THE PRESENT POSITION OF CELL-THEORY. 101

Herbert Spencer followed with his theory of physiological
units. Darwin's theory of pangenesis expressed the same
idea, and more recently Nageli, De Vries, Wiesner, Weis-
mann and others have entered the same or at least similar
objections to the cell-theory. Even Oscar Hertwig, although
he appears in the sentence above quoted to give his
adherence to the view that the cell is a vital unit, abandons
this concept, for all practical purposes, in the latter part of
his book ; for he says, in a most unmistakable manner,
that the cell is an organism composed of ultimate units
which he calls idiosomes.

Each author whose name I have quoted has a somewhat
different account to give of the ultimate constitution of the
cell. But the points on which they disagree are of subor-
dinate importance ; they are all agreed on the main issue,
that the vital activities manifested by the cell are not to be
explained by the visible constitution and structure of the
cell itself, nor by the mere chemical elements of which the
protoplasm of the cell is composed. Each of them avers
that the cell is organised, which means that it is made up of
countless organic units of a lower order, differing among
themselves, and arranged in groups and sub-groups within
the cell in a manner analogous to that in which the cells
themselves are arranged in a composite organism. Since
there is so general an agreement in fundamental principle,
1 am spared the necessity of examining each separate theory
of ultimate vital units in detail ; should anybody wish for a
condensed account of the various theories he will find it in
Weismann's introduction to his work on the Germ Plasm.1

structure d'un ordre plus eleve que la structure atomique des molecules
chimiques des composes organiques non vivants ". No fault can be found
with this definition, but would it not be better to adopt some other term to
express this extra complexity of structure rather than " organisation," which is
inseparably connected with our ideas of the composition of the bodies of
higher animals and plants? For Brucke the organisation of protoplasm
was the same in kind as the organisation of higher animals : for Dujardin
it was something different, and had best be expressed by a different term.
Delage puts the word structure in italics.

1 Still better in Delage's book, referred to further on.

102 SCIENCE PROGRESS.

The point for present consideration is this : Is it neces-
sary for the explanation of vital phenomena to assume
the existence of ultimate vital particles, so minute as
to be invisible with the best microscopical powers
which we possess, each of which is to be considered
as being in posse an independent organism capable of
displaying some of the most characteristic of vital pheno-
mena, viz., assimilation, growth, metabolism, reproduction
by division ?

As it will be necessary to refer frequently to these
assumed vital units, I must call them by some name, and I
shall use Weismann's term biophor, without meaning to
exclude the conceptions of other authors, the pangenes of
De Vries, the plasomes of Wiesner and so forth. I use the
term biophor in the sense of Lebenstrager, the bearer of the
vital properties, without necessarily implying that it pos-
sesses all the particular properties assigned by Weismann
to his biophors.

Whatever the point from which the different authors
have started, they all postulate the existence of minute
biophors on the grounds that the vital phenomena exhibited
by cells, say by an Amoeba, or by the ovum of a Metazoon,
imply the existence of an organisation adequate to the
production of the observed processes. The life processes
are too various and too complicated in their kind to be
explained by the visible constitution of protoplasm, even if
it be allowed, as it generally is allowed, that protoplasm is
not a chemical compound of fixed molecular composition
but a mixture of many chemical substances, each having a
molecular composition of some considerable complexity. I
have already shown that Schwann himself was possessed of
such an idea, which he expressed sufficiently clearly when
he referred to " a peculiar mode of union of the atoms
to form atoms of the second order," but he did not attempt
to follow out the idea, confining himself to the inquiry
into " the arrangement of these conglomerate molecules
when forming either the separate elementary parts of
organisms or the entire organism ". The term consdomer-
ate molecule is in fact synonymous with the term biophor

THE PRESENT POSITION OF CELL-THEORY. 103

in the sense in which I am using it, for the biophor or
ultimate vital unit is held to be an aggregate of chemical
molecules ; the constitution attributed to it is that it is made
up of many different kinds of molecules, just as a molecule
may be composed of several different kinds of atoms. I shall
have to refer aram to the difficulties which still remain if
we accept the hypothesis that a group of different molecules
is able to exhibit the vital functions which are necessarily
attributed to a biophor. Before proceeding to criticism I
must try to give as fairly as I can the grounds for believing
in the existence of biophors. To put the matter as briefly
as possible, the theories of ultimate vital units are the resuh
of attempts to make a mental analysis of living substance
Chemical analysis is impossible, for in the process the
living substance is destroyed as such and becomes dead
substance, possessed of different and much less important
properties. One fact of great importance, however, is
learnt from chemical analysis, and it was appreciated by
Schwann, namely, that, to use his original words, "the
elementary materials of organic nature are not different
from those of the inorganic kingdom " ; hence it has been
inferred, with all reason, that the powers of organic nature
are essentially the same as those of inorganic nature, and
are established by the very existence of matter. It is only
necessary to mention this because there has recently been
a tendency in some quarters to call in the assistance of some
mysterious " vital force " ; a tendency begotten no doubt by
the apparent futility of all attempts to find an explanation
on mechanical and chemical principles of the fundamental
powers of organic nature, assimilation and metabolism.
This, however, need not detain us ; we have to consider
the process of reasoning which, in default of assistance
from chemical analysis, has led so many distinguished
observers and thinkers to analyse the cell into other com-
ponents, and those again into others of a lower grade,
until the biophor, the smallest particle of possible life, is
reached.

The weightiest reason which I have been able to dis-

104 SCIENCE PROGRESS.

cover is given by von Sachs.1 According to this author,
whose views are in agreement with those of Nageli on this
subject, it is necessary for the explanation of certain pheno-
mena exhibited by organic substances that we should assume
the existence of combinations of molecules which form very
large numbers of small particles or micellae as Nageli calls
them. One of the most important of these phenomena is
the imbibition of water. Dry organic substances, such as
gelatine, when placed in water, imbibe it and increase in
volume to a very considerable extent. The increase in
volume produced by the swelling up in water is almost
equal to the volume of water which has been absorbed.
The imbibition of water in such a case is something very
different from the imbibition of water by a porous inorganic
body, such as gypsum, unglazed porcelain, etc. The latter
substances are full of small visible and invisible cavities or
pores, which in the dry state contain air. The water passes
into these cavities or pores according- to the laws of capil-
larity, and in so doing displaces the air, which is forcibly
expelled and can be collected and measured ; there is no
pushing asunder of solid parts, as is shown by the fact that
the porous body is not perceptibly enlarged by the water
which has penetrated into it. But the water penetrating
into gelatine expels no air, it does not enter by capillarity
into spaces previously existent, but forces its way between
the particles of the dry substance, pushing these asunder,
and so causing the considerable increase in volume. The
particles thus pushed asunder are the micellae, and although
they are pushed further apart from one another, they do
not completely lose their connection. Each micella may be
regarded as being surrounded by an envelope of water
when in the moist state ; in the dry state the micellae com-
posing the substance are in mutual contact. This familiar
phenomenon of the swelling of organic substances by the
imbibition of water is contrasted by von Sachs with the
process of solution of a salt. In the latter case the water

XJ. von Sachs, Lectures on the Physiology of Plants, translated by
H. Marshall Ward. Oxford, Clarendon Press, pp. 205 and sq., 1887.

THE PRESENT POSITION OF CELL-THEORY. 105

seizes on the molecules of a crystal and takes them in
between its own molecules ; in the former case the dry
organic body seizes on the molecules of water and forces
them between its own. These reasons are held by von
Sachs and Nageli to be among the weightiest for regarding
protoplasm as an "organised" body, in the sense of being
made up of micellae, and not as being a structureless slime
or fluid.

No doubt they are weighty reasons for regarding or-
ganic substances such as gelatine, starch grains, cell walls,
etc., as being composed of combinations of polyatomic
molecules into groups of a higher order, and there is no
objection to giving these groups a name, such as micellae.
But the admission that such groups exist does not really
bring us much nearer to an explanation of the phenomena
of life. Von Sachs himself points out that even in the
region of pure chemistry it is necessary to assume that
polyatomic molecules are grouped into closer molecular
unions, thus giving rise to chemical properties which did
not belong to the individual molecules.

Gelatine, starch grains and cellulose are not living but
dead substances, and the fact that the behaviour of dead
organic substance finds an explanation on a theory of
micellar structure is but a very small step towards the
explanation of the very different behaviour of living sub-
stance. The micellae may exist in the organic substances
in question, but they are not to be confounded with biophors ;
the very fact that the properties of dead substances may be
attributed to their existence shows that they cannot be con-
sidered as bearers of vital properties.

In point of fact the living substance, which we generalise
under the name of protoplasm, behaves quite differently
in respect of the imbibition of water to the dead substances
which are derived from it. An amoeba or an infusorian,
living in the water, does not imbibe it as a mass of gelatine
would. But when it dies in the same water it immediately
begins to swell up, and eventually bursts and disintegrates.
So that we see that with respect to this very property which
is held to be a reason for assuming a micellar structure of

io6 SCIENCE PROGRESS.

protoplasm, the actual living substance does not exhibit the
property, whilst the same substance when dead does.
Clearly then, the admission that protoplasm has a micellar
structure, that is, that it is composed of minute and invisible
particles consisting of groups of polyatomic molecules, does
not involve the admission that there are ultimate vital units,
biophors, which reside in the cell-like organisms within the
cell-organism. This distinction indeed has already been
made and dwelt upon at some length by Weismann (op.
cit., pp. 41 and 42).

It follows then that whilst we may freely admit that
protoplasm, and also various inert organic substances, are
composed of micellae, and are therefore "organised" in the
sense spoken of by von Sachs, we have still to consider the
evidence for the existence of biophors. At the outset of
this inquiry we meet with a difficulty in that the existence
of biophors is assumed by most authors as a means of ex-
plaining the phenomena of heredity, and this opens up a
wide range of questions into which it is not the purpose of
this essay to enter. But it has well been pointed out by
Wiesner that if minute vital elements occur at all, those
same units which make life possible, and control assimila-
tion and growth, must also be the agents in bringing about
the phenomena of heredity. This view, which commends
itself to everybody, implies that the biophors have only
secondarily acquired historic qualities, and that they are
primarily concerned in the production of the fundamental
processes of life. We may therefore dismiss for the present
purpose the complications introduced by heredity and con-
fine our inquiry to the functions of biophors as bearers of
the essential vital qualities.

It is urged in favour of a theory of biophors that life
must be connected with a material unit of some sort (Weis-
mann) ; that function presupposes structure (Whitman), and
that the structure necessary for the exhibition of such
complicated functions as those of living protoplasm cannot
be of such a simple molecular kind even as the micellar
structure postulated by von Sachs and Niigeli, but must
consist of a definite arrangement, an architecture or organ-

THE PRESENT POSITION OF CELL-THEORY. 107

isation of separate living particles, the aggregate functions
of which produce the vital phenomena. It is further urged
in favour of this view of organisation, that in almost all
cells we are able to recognise structures under the micro-
scope each of which behaves in respect of growth and
multiplication in a manner analogous to that in which the
cell behaves. Not only the nucleus but also the chromatin
bodies, the microsomata of which these are composed, the
centrosomes, the green chromatophores of plant cells, may-
be observed to increase in size, i.e., to grow and to multiply
by division, and it is held that this is proof that the ultimate
particles composing these bodies must assimilate, grow and
divide in a manner similar to that in which cells assimilate,
otow and divide.

This view, whilst receiving a considerable measure of
support from other sources, has been most energetically
supported by Wiesner,1 whose extensive work on the subject
has received the weighty approval of Weismann. Wiesner
refers in detail to the various structures in the form of
granules or corpuscles which may be observed in animal
and vegetable protoplasm, and he attributes to one and all of
them the powersof assimilation and multiplication bydivision.
Nor does he confine himself to the living substance gener-
ally recognised under the name of protoplasm. He labours
at great length to prove that the cell wall, so often con-
sidered as an inert non-living product of living protoplasm,
is not in fact dead, but contains a living substance distin-
guishable under the name dermatoplasm, and ultimately
composed of structural elements of the same fundamental
nature as that of the cytoplasm. These ultimate particles
are the fi/asomes, which form the central point of his theory
of the constitution of living matter. Further than this he
accepts in full the theory of De Vries with regard to vacuoles,
and considers them to be just as much independent organ-
isms as the chromosomes, the centrosomes, the chlorophyll
bodies and other things. This theory of vacuoles, which

1 J. Wiesner, Die Elementar structur und das Wachsthum der Lebendem
Substanz. Wien : Alfred Holder, 1892.

108 SCIENCE PROGRESS.

assumes that they are products of minute bodies called
tonoplasts, is of itself improbable, and is contrary to the
teaching of observations which may readily be made on the
constitution and behaviour of vacuoles in living protoplasm.
It has been shown by Butschli l that the contractile and
other vacuoles of Protozoa continually make their appear-
ance without owing their origin to the division of previously
existing vacuoles. It is not possible to go into details here,
but the reader will find a full discussion of this question in
Butschli's work (p. 230) as also a resume of the various
theories which have from time to time been put forward on
the subject of the granular theory of protoplasm. But even
if peculiar views on the nature of vacuoles be laid aside,
the gist of Wiesner's arguments is not materially weakened.
None of the structures which are observable in protoplasm
are observed to originate neogenetically : they are all, he
says, derived directly by division from pre-existing struc-
tures of similar character. In short, he fully accepts the
aphorism put forward somewhat earlier by Altmann :
" Omne granulum e granulo ". Wiesner does not definitely
say that the various particles observable in protoplasm are
to be severally identified with the ultimate vital units, his
plasomes. Some of them may be individual plasomes, but
the majority of them are, he thinks, aggregates of plasomes,
units of a hioher order which in turn are combined to form
the still higher unit the cell. Thus he presents a scheme
of organisation which, instead of taking the cell as the
lowest structural unit, goes several grades lower ; instead
of the old conception of

organ — tissue — cell,

he represents the scheme of organisation as being

organ — tissue — cell — granules — plasomes.

A detailed criticism of Wiesner's views would occupy a

much larger space than I have at my disposal, and such a

criticism is unnecessary, since all that need be said has

1 O. Butschli, Investigations on Microscopic Foams and Protoplasm.
Authorised translation by E. A. Minchin. London : A. and C. Black,
1894.

THE PRESENT POSITION OF CELL-THEORY. 109

already been set forth by other authors in their criticisms of
similar theories, particularly by Biitschli {loc. cit., p. 195)
and O. Hertwig, both of whom occupy themselves with
Altmann's views, which are to all intents and purposes
identical. Only a few of the most important points need be
touched upon here.

It is certainly a remarkable fact, and confirmed by
abundant experience, that many of the constituent parts of
cells are produced by divisions which recall the divisions of
the cell itself. The nucleus is the most important and the
most familiar constituent of the cell : it is within the experi-
ence of every biologist that nuclei are never observed to
originate neogenetically, but always by division of a pre-
existing nucleus. The chromatin elements of the nucleus may
be shown to be composed of minute particles, the so-called
chromosomes, and these reproduce themselves by division,
and are never observed to originate neogenetically. The
same statement holds good for the centrosomes, for
chlorophyll corpuscles and for various kinds of chroma-
tophores. It is not to be denied that these facts, which
become more and more familiar to the working microscopist,
appear to lend a powerful support to the theory of
biophors ; in a limited sense they may be said to be a proof
of the statement that the cell is an organised body.
Whether, as Wiesner claims to be the case, there are many
other constituents of cells which similarly reproduce their
kind by division, and are never observed to originate
independently, may for the present be left out of considera-
tion. The evidence that amylum grains and granules of
various kinds behave like the centrosomes in this respect, is
as yet too slight, and the observations are too conflicting to
enable us to come to a judgment without entering into a
mass of detail which is not wholly relevant to the question
at issue. But there is at least one criticism which is worthy
of mention, namely, that of Biitschli, who points out {loc. cit.,
p. 200) that among the strongly staining granules of proto-
plasm there are bodies which are not actually constituents
of the protoplasm but are symbiotic micro-organisms.
The existence of such organisms, which have been called

no SCIENCE PROGRESS.

Bacterolds, has been frequently demonstrated in animal
and vegetable cells, and Biitschli points out that granules
similar in appearance to bacteroids occur in the Vorticellinse
and may be observed at certain times to be in a state of
rapid proliferation.

Just before writing these pages I have been shown
preparations exhibiting the numerous bacteria symbiotic
in Pelomyxa, and it is very possible that the rapid
proliferation of bacteroids has been mistaken by various
observers for the reproductive activity of granules forming
an integral part of the cell. It is almost certain that the
mistake has been made in some cases, and until further
investigation has increased our knowledge of the various
micro-organisms which are symbiotic or parasitic in cells, it
is well to be somewhat sceptical of statements regarding
the divisional processes of cell contents. It would seem then
that our present knowledge does not justify our regarding
all the particles of a cell as originating in a similar manner
from the division of pre-existent similar particles, though
we must affirm in the most positive manner that some few
of the constituents of the cell originate in this way only, and
are never produced de novo. The question now to be
considered is this : must we, because these bodies (the
centrosomes, chromosomes, etc.) assimilate, grow and
reproduce themselves by division, regard them as indepen-
dent vital units? A cell exhibits these phenomena and the
cell is regarded as an independent unit in posse, if not
actually in esse ; must we therefore attribute to all bodies
exhibiting the same phenomena the character of indepen-
dent units ? The answer, I believe, is very decidedly no.
Cells would never have been regarded as independent units
if they had merely been observed to assimilate, grow and
divide, whilst retaining their connection with other cells
undergoing the same processes. The quotations which
I have given from Schwann's work show that the
theory that the cell is an independent life unit was not
founded on the fact that it assimilates, grows and divides, —
Schwann indeed overlooked the phenomena of reproduction
by division — but upon the fact that cells are capable of

THE PRESENT POSITION OF CELL-THEORY, in

leading an independent existence. This is so important a
part of the cell-theory that I may again quote in his own
words Schwann's reasons for calling the cell an elementary
unit of life. " Now if we find that some of these elementary
parts not differing from the others are capable of separating
themselves from the organism and pursuing an independent
growth, we may thence conclude that each of the other
elementary parts is already possessed of the power to take
up fresh molecules and grow, and that therefore each
elementary part possesses a power of its own, an indepen-
dent life."

In the case which we are considering the very faculty
which was so powerful a reason for regarding cells as
independent units is wanting. Nobody has ever observed
a nucleus or a centrosome or even a chromatophore to
separate itself from the cell and pursue an independent
existence. And not only is there no recorded case of the
constituent particles of cells separating themselves spon-
taneously from the cell, but experiments which have been
made with the express purpose of determining whether
these particles can live apart from the cell to which they
belong have in every case given a negative result. Even
the nucleus, highly complicated as it is, and itself composed
of smaller particles which may easily be demonstrated,
perishes when removed from the cell body. The chroma-
tophores similarly perish, and so no doubt would the
centrosomes if it were possible to isolate such very minute
particles. Many instances might be cited in proof of this,
but it is scarcely necessary to bring forward the details ;
the reader can obtain them by reference to the works of
Nussbaum,1 A. Gruber and Verworn.2

It is of some interest in this connection to contrast the
process of reproduction in unicellular and multicellular or-
ganisms. In the latter reproduction is effected by the
separation of a single unit, a cell, from the aggregate, and

1 M. Nussbaum, Biol. Centralblatt, vol. iv.

2 Max Verworn, " Die physiologische Bedeutung des Zellkerns,"
Pfliiger s Archiv, vol. li., 1892.

ii2 SCIENCE PROGRESS.

the unit so separated has from the time of its separation an
independent individuality and eventually reproduces the
aggregate. The fact that the union of two cells is commonly
necessary for the maintenance of life and the exhibition of
the powers of development, need not be urged as an objec-
tion to this simple statement of the case, for the facts of
parthenogenesis show that the union of two cells is not an
essential feature. Now if we adopt Wiesner's scheme, and
imagine that organisation does not stop at the cell, but that
beyond this there are granules, and beyond these again
plasomes, and that the plasomes stand in the same relation
to the cell that the cell stands to the multicellular organism ;
we should expect to find that in the reproduction of
monocytial organisms the plasome plays a part anal-
ogous to that played by the cell in the reproductive
processes of polycytial organisms. But we find nothing
of the kind. The monocytial organism reproduces itself in
just the same way as the polycytial, by the separation of a
cell, complete in all its parts. There is no such thing
known, even in cases where a flagellate or a radiolarian
breaks up into innumerable particles or spores of extreme
minuteness, as the separation of any one individual con-
stituent of a cell possessed of the power of leading an in-
dependent existence and in time of reproducing all the other
constituents. Every spore, however minute, has its portion of
the cytoplasm and its share of nuclear matter. If there are
any other constituents, it probably has its share of these
also, but one cannot speak with certainty on this point, for
positive evidence is wofully deficient. At any rate Wiesner,
holding fast to his theory that nothing, not even an amylum
or an aleurone grain, is produced neogenetically, is at great
pains to prove that in cellular reproduction all the parts
of the parent are transferred to the offspring. Assuming
that this is so, and remembering that there is abundant
evidence that nuclear matter and cytoplasm are always
transferred, it is evident that the relation in which the
plasomes or biophors, regarded as ultimate vital units,
stand to the cell, is not at all the same as the relation in
which the cell, regarded as an ultimate unit, stands to the

THE PRESENT POSITION OF CELL-THEORY. 113

polycytial organism. Biitschli, in a short but very weighty
sentence,1 brings forward the same argument that I have
just used in opposition to Altmann's theory of the part
played by granules in the vital processes of protoplasm. In
my judgment the argument as far as it goes is a sound
one, but I am aware that it does not altogether refute the
theory of biophors, but only that part of it which states that
as cells are to polycytial aggregates so are biophors to cells.
This refutation, however, seems to me to be a considerable
gain. For it enables us to apprehend that the structure or
constitution of the cell, whatever it may be, is not to be ex-
pressed in the same terms as the structure of the higher
organisms.

It may be objected that nobody does express the
structure of the cell in such terms, but the objection does
not hold good. It is true that most authors are more
guarded in their expressions than Wiesner, and evade the
responsibility of declaring that the biophor is to the cell
as the cell is to the polycytial organism, by means of re-
servations, couched for the most part in terms so ambiguous
and even transcendental that the whole issue is involved in
an obscurity from which it seems hopeless to try to escape.
But these expedients are really of little use. The fact re-
mains that in every case the fundamental idea is the same,
that the phenomena exhibited by isolated cells having an
independent individual existence are of essentially the same
kind as the phenomena exhibited bypolycytial organisms and
must be explained on the same grounds.

If it be not so, what is the meaning of the argument
which was first put forward in definite shape by Brlicke,
and has been repeated by every author who attacks the
question in the same manner that he did, that the com-

1 " So long as the individual constituents of the cell are not seen to
persist when isolated, nor are distinct living phenomena observed in them,
it is very dangerous to speak of their life as something which they possess
in themselves. They are so far living, as long as the opposite is not proved,
in that they are parts of living organism, so that the granula may be
living in the same way as the nucleus, even though they no longer betray
any sign of life after isolation" (Joe. eit., p. 199).

8

ii4 SCIENCE PROGRESS.

plexity of the phenomena exhibited by individual cells, say
by an amceba, is so great, the functions observed are so
many and so various in their kind that they can only be
explained by the assumption that protoplasm is an organised
body ? Taking the words of O. Hertwig as a fair ex-
pression of current opinions on the life processes of a poly-
cytial organism, " that the aggregate life processes of a com-
posite organism appear to be nothing more than the ex-
ceedingly complicated result of the individual life processes
of its numerous and variously functional cells," it is evident
that to the minds of Briicke and his successors the aggre-
gate life processes of the corpuscle of protoplasm called a
cell are nothing more than the highly complicated result of
the individual life processes of its numerous and variously
functional biophors. If they do not mean this, I am quite
at a loss to know what they do mean, or to understand the
relevancy of the so-called axiom laid down by Whitman,
that "function presupposes structure," or the meaning of
the statement expressed so often and with such obvious
satisfaction, that " the cell is an organism ". These sen-
tences, so terse and so epigrammatic, exercise a peculiar
fascination over most minds. To understand their exact
applicability to the question at issue they must be carefully
examined. Function presupposes structure. To the bio-
logist who makes a rapid mental survey of his experiences,
this appears to be a generalisation of universal truth.
Physiology, which draws its inferences almost exclusively
from the study of the higher animals, tells us that ultimately
every function of the composite organism is to be referred
to a particular group of cells, and that cells differ in kind
according to the different functions which they exhibit. So
much is this truth forced upon us that if conceivably a new
function were to make its appearance, we should immediately
search for the cell groups appropriate to the performance of
that function. So far so good, but before proceeding further
we must take note that the statement that function pre-
supposes structure is a generalisation founded on experience.
It is not an axiom as Whitman calls it, for an axiom is a
proposition which is self-evident, and this assuredly is not.

THE PRESENT POSITION OF CELL-THEORY. 115

The next step is to transfer this generalisation, founded on
experience, into a new region, to the functions of cells. In
order to do this we should possess the same experiences
with regard to the functions of cells which we possess
with regard to the functions of composite organisms. But
these experiences are entirely wanting. We observe that
protoplasm exhibits functions, that it assimilates, that it is
irritable, that it is contractile, that it is reproductive, and so
forth ; but who has been able to demonstrate or even to
suggest with any plausibility that there are structures
specially devoted to assimilation, to contractility, to irrit-
ability, and to reproduction in protoplasm? It is evident
that the absence of any such experiences has been felt by
many observers, who have accordingly studied protoplasm
with a view to finding the required structures, and some
are inclined to say that the nucleus or perhaps the centro-
some is reproductive, the amylum and aleurone bodies are
assimilative and so forth. But there are protozoa endowed
with active functions which have no centralised nucleus ;
the presence of centrosomes has yet to be demonstrated in
protozoa in general, and there are forms in which, as
Biitschli well points out, the protoplasm is homogeneous,
e.g., in the pseudopodia Gromia dujardini} The reader
should refer to Biitschli's work for a discussion of the sub-
ject of hyaline protoplasm (loc. cit., p. 262). The fact that
it exists is of the highest importance, for it shows that there
is living substance exhibiting the usual vital phenomena of
assimilation, contractility, etc., which, nevertheless, defies
all attempts to recognise an organisation which in the light
of previous experience would seem adequate to the effects
produced, and it shows also that the centrosomes, the
amylum grains, and their analogues, and the whole category
of granules are secondary phenomena, which may be

1 Not only are there no granules in homogeneous protoplasm, but the
alveolar structure of it is unrecognisable. It is easily shown, however, that
the homogeneous substance is produced from alveolar protoplasm and is
capable of reconversion into it. The physical explanation of the dis-
appearance of the alveolar structure is given by Biitschli on p. 264 of the
English translation of his work.

n6 SCIENCE PROGRESS.

altogether absent and yet the life processes go on un-
changed.

It must be confessed then, that the experiences which
so amply justified our generalisation when applied to com-
posite organisms are altogether lacking when we seek for
a justification for applying it to the simplest unicellular
organisms. Moreover I have just shown that in one im-
portant particular at least, we do not merely lack these
experiences, but that we have experiences of an entirely
different kind. In face of this is it not obvious that the
captivating generalisation must be abandoned altogether in
the region which we are now discussing ? For it is founded
on experience, and where experience fails or is contradictory
the generalisation fails also.

After what has already been said it is unnecessary for
me to enter into a detailed examination of the other state-
ment which is considered to mark a great advance in bio-
logical thought, that "the cell is an organism". It is
sufficient to say that if this proposition means anything at
all, it means that the cell has an organisation which is
similar in kind to that of a composite organism of which a
cell is a part. If I am told that it does not mean this, but
something else, then I ask, firstly, what does it mean ? And,
secondly, if it does not mean this, what necessity is there for
assuming that the protoplasm of the cell is built up of bio-
phors, the biophor being the elementary living constituent,
assimilating, growing and dividing, taking up definite posi-
tions in the cell, combining with others like or unlike itself to
form higher aggregates, and so impressing a fixed archi-
tecture on the cell of which it is a component ? Why, in
short, if the statement does not mean that the organisation
of the cell is the same in kind as the organisation of a
composite animal, why then does everybody who believes
that the cell is an organism ascribe to it an organisation
which is the same in kind as that of the higher animals ?

The fact is, and it is patent to everybody, that most
authors do conceive of the cell-organisation as being the
same in kind as the organisation of higher animals. They
either have the courage of their opinions, like Wiesner,

THE PRESENT POSITION OF CELL-THEORY. 117

and say so in so many words, or they tacitly admit it by
their description of what they conceive cell-organisation to
be. They are dominated by the cell-theory. Mr. Adam
Sedgwick has recently said that the cell-theory is an incubus
which perverts the minds of biologists, whose minds are so
saturated with conceptions borrowed from the cell-theory
that they are unable to see anything else. I have else-
where found fault with this statement, but when the theories
of cell-organisation are considered, I must freely confess
that he has right on his side. Not only does the zoologist
believe "that the cell is the unit of structure, and that it
forms the basis of organisation in the metazoa," but he also
believes that some correlative of the cell forms the basis
of all organisation whatsoever. His eyes are " blinded to
the most patent facts" by ideas derived from the cell-theory,
and it is not too much to say that the theory does " obstruct
the way of real progress in the knowledge of structure ".
Whether consciously or unconsciously the believer in bio-
phors starts with ideas derived from the cell-theory, he
tacitly assumes the universal applicability of the proposition
that function presupposes structure, and he seeks to explain
the functions of protoplasm by attributing to it an organisa-
tion which in all essential characters is the equivalent of
the organisation of the metazoa. Since I have just shown
that there is no justification for transferring a generalisation
based upon experience to a region in which experience is
either wholly wanting or, if present, of a different kind, it is
hardly necessary for me to elaborate and show that it is
equally unjustifiable to attribute to the unknown a plan of
organisation identical in kind with the plan which we have
learnt by experience to recognise as the attribute of the
known.

Some time ago I pointed out that there was a fallacy in
the word organism.1 Whitman has ridiculed the statement,
yet the more I reflect upon it the more I am convinced
that the fallacy exists, and that it is in the highest degree
mischievous and misleading. By an organism we mean

1 G. C. Bourne, " Epigenesis and Evolution," this journal, vol i., 1894.

n8 SCIENCE PROGRESS.

either an independent living thing, in which case the term
is loose but applicable to every animal in the monocytial
stage, or we mean a thing possessing organisation, and by
organisation we mean a certain structural plan, the idea of
which is a generalisation from our experience of animal and
vegetable structure in general. That this is historically
and in fact the connotation of the term organisation is in-
dubitable.1 When we use the term organisation we
either use it in this connotation or in some other. If we
use it in the same connotation with respect to protoplasmic
structure, we are consistent, but, as I have shown, we are
applying ideas derived from one set of phenomena to
another set of phenomena to which they are not appropriate.
But if we use it with another connotation, then we expose
ourselves at once to the risk of the well-known fallacy which
is inseparable from the use of the same term with different
connotations. If the two connotations are clearly defined
and generally understood, the fallacy may be avoided,
though the inconvenience remains ; but if the one connota-
tion is clear and definite whilst the other is vague and
ambiguous in the highest degree, no amount of circum-
spection will prevent our falling into the fallacy almost at
the first opportunity. This is exactly the case with the term
organisation. In the one sense we know its connotation
exactly, and when authors use it in that sense they have,
in the course of their arguments, to adhere strictly to the
technical sense of the word. Most of them do this, for
they are aware of the absurdities and inconsistencies into
which they would fall if they did otherwise. But what
of those who use the term with another connotation ? They
assure us that it does not denote a plan of structure like in
kind to that of the metazoa : what then does it denote ?
Something so vague, so unreal and unsubstantial that we

1 Thus in Worcester's Dictionary of the English Language, 1881 : —
Organisation. The condition of an organised body or the totality of

parts which constitute and the laws which regulate an organised body.

Organised. Formed with organs : composed of several individual parts

or organs, each of which has its proper function and conduces to the

existence of the entire system.

THE PRESENT POSITION OF CELL-THEORY. 119

are even at a loss to know to what to apply it ; its connota-
tion has never even been attempted. The futility of using a
term without connotation and with the most vague denotation
is so well illustrated by the following passage from Whit-
man that I cannot refrain from introducing it here : " When
we speak of the organisation of the germ as cut directly
from a pre-existing parental organisation of the same kind
we are not thinking of the definitive organisation which
belongs to the fully formed organism, but of that primary
organisation which belongs to the protoplasm itself". This
raises our expectations, we are going to hear something of
the primary organisation which belongs to protoplasm itself.
Whitman continues: "We are so accustomed to connect
the idea of organisation with the anatomical organs of the
adult that we are apt to forget that there is a primary
organisation which underlies every anatomical organ. The
germ has this primary organisation ; it is therefore an
organism, and as such may dominate its own development."
From which weighty and sententious passage we gather
that the germ is an organism because it has a primary
organisation which is not the definitive organisation which
belongs to the fully formed organism, but a primary organ-
isation which belongs to protoplasm itself. What on earth,
we may well ask, is this primary organisation ? The
answer is given on the same page. It is "that original
constitution of the germ which pre-determines its type of
development and the form which ultimately distinguishes it
from other species developing under like external conditions".
The terms "original constitution" and "primary organisa-
tion " are merely synonyms. So we learn that the primary
organisation so important to those who have more thought-
fully scanned the gap between the cell and the physical
molecule, is the primary organisation of the germ, which
pre-determines its type of development, etc. I hope that
others are satisfied by this most remarkable piece of
scientific exposition. For myself I must humbly confess
that I am none the wiser for it, any more than I should be
if I asked what was a Megalosaurus and I was told : "A
Megalosaurus, why you know it is a big lizard, it is — a — a

120 SCIENCE PROGRESS.

Megalosaurus in fact ". Nor is confusion less when I am
told in one sentence that the organisation of the germ cut
directly from pre-existing parental organisation of the same
kind is not the definitive organisation which belongs to the
fully formed organism, but is that primary organisation
which belongs to protoplasm itself, and I read in the
sentence immediately preceding that " the essential thing is
not simply continuity of germ substance of the same
chemico-physical constitution, but actual identity of germ-
organisation with stirp-organisation ". The organisation of
the germ is identical with the organisation of the stirp, and
yet the organisation of the germ is not that of the fully
formed organism, but is a primary organisation which
belongs to protoplasm itself. What does it all mean ? It is
different and yet it is identical, and it is organisation, organisa-
tion, toujours organisation. I beg Dr. Whitman, for pity's
sake, to descend from his altitude, scarcely dreamed of in the
philosophy of Harvey and Wolff, and to condescend to
inform a poor bewildered mortal, who confesses to a pre-
judice in favour of things which he can understand, what
this wonderful primary organisation is.

Seriously speaking I believe that organisation either
means a plan of structure of the same type as the structure
of higher animals and plants, and capable of being described
in intelligible terms as it has been by Weismann, Wiesner
and others, or it means nothing at all ; it is a mere phrase
which seeks to cover but does not conceal our ignorance.

G. C. Bourne.
( To be continued. )

SOLID SOLUTIONS.

IF we define solutions as homogeneous mixtures of sub-
stances in variable proportions, we are at once obliged
to admit the existence of solid solutions, for there are many
mixed solids which fulfil the requirements of this definition.
Common potash alum, for example, can crystallise together
with ammonia alum, and form mixed crystals which are
perfectly homogeneous and of the same composition through
out, although the proportions of the two constituents may
be varied at will by proper selection of the aqueous solution
from which the crystals separate.

We are inclined, however, to look in solutions for some-
thing more than mere homogeneity and uniformity of com-
position, and perhaps one of the most obvious characters of
a liquid solution is this, that should it at first be of different
composition in different parts of its mass, there is always
present the tendency of the dissolved body to attain a uni-
form distribution throughout the solvent. The process of
equalisation of the composition, or diffusion, occurs in all
solutions which are more concentrated in one part than in
another, the dissolved substance moving from the place of
greater to the place of less concentration. Diffusion in
solution goes forward very slowly if the liquid is protected
from mechanical disturbance and sudden change of tem-
perature, months being requisite for the attainment of uni-
form concentration if a comparatively short column of pure
solvent is placed above a denser layer of strong solution
contained in the bottom of a cylinder. If diffusion takes
place in solids we might expect it to proceed even more
slowly.

A class of substances which form in some sort a connect-
ing link between liquids and solids, and are specially suited
to the study of diffusion phenomena, is to be found in jellies.
Graham, to whom we owe our first exact knowledge of
diffusion in liquids, prepared a stiff jelly containing common
salt in solution in one part, and compared the rate at which

122 SCIENCE PROGRESS.

the salt diffused in it with the rate at which salt dif-
fused in pure water. He found that the diffusion in the
jelly took place almost, if not quite, as fast as in water
itself. The composition of the jelly was 2 per cent, gelose
and 98 per cent, water, so that, as far as actual substance
was concerned, the salt had to meet practically the resistance
of water alone in both cases, and the experiment showed
that the mere change in apparent condition of the whole
mass had little or no influence on the rate of diffusion.
Subsequent experiments have served to confirm Graham's
results.

When we pass to solids proper we find that instances
are not wanting of what is apparently diffusion within them.
Van't Hoff in his fundamental paper on solid solutions gives
numerous examples. In the preparation of steel by the cem-
entation process bars of wrought iron are packed in charcoal
and subjected to a red heat for several days. The charcoal
gradually penetrates the iron and converts it into steel. It
matters little for our purpose what the particular form is that
the carbon assumes during its passage through the iron — in
some fashion or other it reaches the centre of the dense bar.
The distribution of the carbon, too, if the operation is inter-
rupted before uniformity has been attained, is precisely what
would be expected if the phenomenon were one of real diffu-
sion ; and the influence of time is the same in both processes.
Not only has carbon been observed to pass through iron,
but it has even been proved to travel slowly through por-
celain, when porcelain crucibles have been heated in a bed of
graphite.

When a metal such as copper is deposited galvanically
on another metal, it penetrates beyond the surface of the
latter into its substance, and zinc objects which have been
lightly coppered are, even when protected by a coating of
varnish, occasionally observed to become white again
owing to the gradual mixing of the two metals near the
surface.

Professor Spring, of Liege, who has devoted special
attention to the chemical behaviour of solids under high
pressure, has supplied some interesting instances of pheno-

SOLID SOLUTIONS. 123

mena which can only be explained by the assumption of
solid solutions. When equivalent proportions of barium
sulphate and sodium carbonate are finely powdered,
intimately mixed, and subjected to a very high pressure, a
double decomposition takes place with formation of barium
carbonate and sodium sulphate. The decomposition, how-
ever, is not complete, only 20 per cent, of the original
substances being transformed. If, on the other hand, we
start with a mixture of barium carbonate and sodium
sulphate and compress it, we find that the reverse trans-
formation now occurs, barium sulphate and sodium carbonate
being formed, and that to the extent of So per cent, of the
original substances present. Here we are evidently dealing
with a state of equilibrium between the four substances
above mentioned, which can only exist together permanently
under pressure in certain definite proportions. If these
proportions are departed from, the system so transforms
itself that the requisite state for equilibrium is attained.
Now this of itself points to the substances existing here in
a state analogous to that of bodies in liquid solution, for we
know that in general definite proportions are necessary in
solutions for stable equilibrium to exist. In the case of
solids the general rule is that when they are in equilibrium
under given conditions in one proportion, they are in
equilibrium under the same conditions in every other pro-
portion. The behaviour, then, of these solids under pressure
is analogous to the behaviour of substances in solution, and
different from the ordinary behaviour of solids. The con-
tinuance of the pressure is not essential to the establishment
of such a definite solid equilibrium, for Spring has shown
that by relieving the pressure after 73 per cent, of a
system of barium carbonate and sodium sulphate had been
transformed, the process continued, though less rapidly,
and after a week had reached the proportion of 80 per cent,
necessary for equilibrium. Here diffusion must have played
a part, for no matter how finely divided the reacting sub-
stances originally were, their surface of contact (where alone
the mutual decomposition could take place if there were no
diffusion) must have been comparatively small.

124 SCIENCE PROGRESS.

It is well known that some metals have the property of
allowing certain gases to pass through them under favourable
conditions, the most thoroughly investigated instance of
this kind being the permeability of the metal palladium to
gaseous hydrogen at moderately high temperatures. At
about 300° C. hydrogen can pass quite freely through a
palladium septum, and it is difficult to conceive the nature
of this phenomenon without admitting the existence of
diffusion in the solid. Whether the hydrogen is dissolved
in the palladium or forms a compound with it, as has been
asserted, is of little consequence, for in the latter case the
compound superficially produced must have possessed the
power to penetrate the remaining metal, or to allow of the
passage of hydrogen through itself.

Connected with the process of diffusion in solution we
have the phenomena of the conduction of electricity in
solutions, or electrolysis. Here the electric current is
carried by material particles, and the resistance that these
experience in their passage through the solution is of the
same nature as the resistance offered to diffusion. Helm-
holtz, in his Faraday lecture, drew attention to the fact that
glass behaves as an electrolyte towards an electric current,
i.e., that the current in passing through the glass is as-
sociated with two currents of particles moving in opposite
directions. The particles travelling towards the negative
pole of the battery have since been proved to move faster
than those moving towards the positive pole. Lehmann
also has shown that when two silver electrodes are immersed
in fused iodide of silver, which is afterwards allowed to
solidify, and a current of electricity is passed through the
solid iodide, one of the electrodes increases in weight at the
expense of the other, and that the phenomenon can be
reversed by reversing the current.

These examples will suffice to indicate that we are not
without data to establish an analogy between the behaviour
of certain solids and the behaviour of ordinary liquid solu-
tions. Since the appearance of van't Hoff's original paper
on the subject a considerable number of researches have
been published more or less directly bearing on the question,

SOLID SOLUTIONS. 125

but the results achieved have on the whole been small, owing
chiefly to the experimental difficulties encountered.

An important application of the idea of solid solutions
was made by van't Hoff in explaining the abnormalities
that are sometimes met with in the determination of mole-
cular weights by the lowering of the freezing-point in solu-
tions. It had been proved theoretically that the freezing-
point of a given solvent should be depressed to a certain
value (calculable from the freezing-point and the latent
heat of fusion of the solvent) when the solution was of
normal concentration, i.e., contained one gram-molecule
of dissolved substance per litre. The nature of the dis-
solved substance should be without influence on this value.
Now, whilst it was ascertained experimentally that this
theoretical relation was in the vast majority of cases ac-
curately fulfilled, yet there remained certain combinations
of dissolved substance and solvent which gave values of the
depression constant altogether at variance with the cal-
culated value. Thus, metacresol dissolved in phenol gave
a depression of 48 instead of 74, and thiophene dissolved in
benzene a depression of 34 instead of 53. Van't Hoff's
explanation of these and similar abnormally low values of
the depression was that the freezing-point observed was not
in the strict sense the freezing-point which had been assumed
in the theoretical reasoning. The true freezing-point of a
solution is the temperature at which the liquid is in equi-
librium with the solid solvent. The freezing-point of an
aqueous salt solution, for example, is the temperature at
which it can exist in contact with pure ice without the ice
melting or without fresh ice being deposited from the solu-
tion. Now, in the exceptional cases above alluded to it is
known that the solid and the solvent have a tendency to
crystallise together, i.e., to form mixed crystals, so that the
substance that separates out is not the pure solvent but
rather a solid solution. The temperature at which such a
solid solution would be in equilibrium with the liquid solu-
tion might not by any means be the freezing-point of the
solution as above defined. The apparent observed freezing-
point of the solution, therefore, would not in general coincide

126 SCIENCE PROGRESS.

with the calculated depression, and van't Hoff from theo-
retical considerations showed how the divergence could be
estimated from a knowledge of the composition of the solid
which actually separated out from the solution on cooling.
That the abnormal values for the points of solidification
depend on the separation of the dissolved substance along
with the solvent has now been experimentally verified in a
considerable number of cases. Heycock and Neville found
that for the case of solutions of antimony in molten tin, the
freezing-point of the tin was raised instead of lowered by
the presence of the second metal. Kiister has shown that
this and similar instances are susceptible of a very simple
explanation. The two metals separate out together in very
nearly the same proportion as that in which they remain
behind in the liquid, so that the solution solidifies as a
whole. In such circumstances the point of solidification of
the liquid can be calculated by the simple mixing formula.
If the melting-point of each pure substance is multiplied by
the proportion in which it exists in the mixture, the sum of
the two numbers thus obtained will give the point of solidi-
fication of the solution. As antimony melts 200 degrees
higher than tin, the admixture of the former in however
small proportion will, since the mixture freezes as a whole,
raise the point of solidification instead of lowering it, as
would be the case if pure solid tin separated from the liquid
on cooling.

Not only do solutions exhibit a lower freezing-point than
that of the pure solvent, but they also exhibit a lower
vapour tension. The pressure of aqueous vapour over
salts containing water of crystallisation may in many cases
be measured with accuracy, and there it is found that the
isomorphous admixture of another salt lowers the vapour
pressure of water which is in equilibrium with the solid.
Thus the vapour tension of a mixed crystal of ordinary alum
with iron alum is less than the vapour tension of either of
its components. In this respect then the mixed crystal
behaves as a solid solution. Again, the solubility of a sub-
stance is diminished when it itself acts as a solvent for
another substance insoluble in the original solvent. Of the

SOLID SOLUTIONS. 127

three liquids, ether, water, and benzene, ether and water are
partially miscible, benzene and water are immiscible, and
ether and benzene miscible in all proportions. Suppose we
take water as the original solvent — then on shaking it up
with ether we find that the latter dissolves to a certain
definite extent in it, i.e., possesses a certain solubility
in water. If now we previously dissolve benzene in the
ether which we shake up with the water, we find that the
water will now take up less ether than before. The solu-
bility of ether in water is thus diminished when benzene is
dissolved in it — and this behaviour is characteristic of all
such combinations of substances.

A case of this kind where two solids play the part of the
ether and benzene in the previous instance has been
thoroughly studied by F. W. Klister. The solid hydrocarbon
naphthalene is, like the hydrocarbon benzene, insoluble in
water ; /3-naphthol, on the other hand, is, like ether,
sufficiently soluble in water to permit of accurate estimation.
But naphthalene and /3-naphthol can crystallise together in
any proportion so as to form a complete series of isomor-
phous mixtures, the melting-points of which vary according
to the rule given above for mixtures of antimony and tin.
A comparison of the amount of /3-naphthol dissolved by a
given quantity of water from such mixtures led to some-
what unexpected results. Instead of the addition of a
small quantity of naphthalene to /3-naphthol lowering the
solubility of the latter in water, it was found that mixtures
containing as much as 30 per cent, of naphthalene had
precisely the same solubility as /3-naphthol itself. As more
naphthalene was added the solubility increased slightly,
afterwards to diminish continuously to zero as the mixture
was made to contain more and more naphthalene. The
explanation of this behaviour suggested by Klister is that
naphthalene and /3-naphthol are capable of forming a chemi-
cal compound consisting of one molecule of each substance,
this compound being decomposable by water, an assumption
by no means improbable, as many similar cases have been
observed. If we allow further that the solubility of the
compound is greater than the solubility of /3-naphthol, the

128 SCIENCE PROGRESS.

results are satisfactorily accounted for. The diminution
of solubility when much naphthalene is present is the
normal depression of the solubility of the compound by
the addition of excess of naphthalene. The solubility
greater than that of pure naphthol is the solubility of the
compound naphtholnaphthalene. The constant solubility
(equal to that of /3-naphthol) observed when there is little
naphthalene in the mixture is the solubility of /3-naphthol,
for the naphthalene in the mixture is in the form of the
compound naphtholnaphthalene, which is decomposed at
the surface by water into naphthalene and /3-naphthol,
which exist now alongside of each other and not in the
intimate union of a crystalline isomorphous mixture.

In connection with the results of these experiments
Klister is inclined to make a distinction between crystalline
isomorphous mixtures and solid solutions proper, because in
the former there is practically no diffusion owing to what
may be termed the rigidity of the crystalline structure.
He admits, however, that no absolutely sharp line can be
drawn, as there are various intermediate degrees in which
diffusion may take place. A reference to the examples of
diffusion in solids previously cited in this paper will show
that they all occur in amorphous bodies without any regular
structure.

A point of considerable interest in the theory of solid
solutions is that it affords us the possibility of determining
molecular weights of the dissolved substances, and since in
isomorphous mixtures we usually attribute similarity of
molecular structure to the two components, we can also in
this case form an estimate of the molecular weight of the
solid solvent. From his experiments on the amount of /3-
naphthol dissolved by water from mixtures of that substance
with naphthalene, Kiister was able to calculate with a high
degree of probability the molecular weight of each of these
substances in the solid state. In the first place he found
that with mixtures containing excess of naphthalene the
ratio of the square root of the concentration of /3-naphthol
in the solid mixture to the concentration in the aqueous
solution saturated by that mixture was very nearly constant,

SOLID SOLUTIONS. 129

varying but little with the actual composition of the mixtures
taken. The general theory of solutions asserts that when a
substance(here /3-naphthol) is divided between two immiscible
solvents (here water and naphthalene, or naphtholnaph-
thalene) it will be distributed in a constant ratio between
the two solvents, no matter what amount of it be taken,
provided only the molecular weight of the substance is the
same in both solvents. In the case investigated this does
not hold — the ratio of the concentrations in the two solvents
is not constant ; and the molecular weight of /3-
naphthol dissolved in water is therefore different from the
molecular weight of /3-naphthol " dissolved " in naphthalene.
The theory further asserts that when, as in the present
instance, the concentration in one of the solvents is pro-
portional to the square root of the concentration in the
other solvent, the molecule in the second solvent must be
twice as great as the molecule in the first. We know that
/3-naphthol dissolved in water has the normal molecular
weight corresponding to the formula CIOHsO ; in naphthalene
solution it has consequently the molecular weight corre-
sponding to the formula (CIOH80)2.

The theory of solutions likewise enables us to calculate
the molecular weight of the naphthalene in the above
experiments from the diminution of the solubility of the
/3-naphthol in water as it dissolves more and more naph-
thalene. In the case before us the question is slightly com-
plicated by the existence of naphtholnaphthalene molecules,
but Kiister was able to arrive at the result that naphthalene
must have double the molecular weight in the state of solid
solution that it has in the state of vapour, viz., (CIOH8)2.

Another well-investigated case of solid solutions is that
offered by the absorption of hydrogen by palladium.
T roost and Hautefeuille, in order to obtain information as to
the state in which the hydrogen existed within the metal,
made an extensive series of observations of the pressure of
hydrogen in equilibrium with palladium containing different
amounts of hydrogen. They found that with compositions
of the solid up to one atom of hydrogen to two atoms of
palladium the pressure of hydrogen remained constant

9

i3o SCIENCE PROGRESS.

at ioo° C, after which it increased rapidly as the pro-
portion of hydrogen in the solid increased. The analogy
between this case and the case of the solubility of mixtures
of /3-naphthol and naphthalene in water is at once apparent.
In both instances we have constancy of pressure (gas-
tension) and solubility (solution-tension) within a certain
range of composition, and then rapid variation with further
change of composition. The conclusions arrived at in both
instances are also similar. The constant solubility was
attributed by Klister to the formation of a compound
naphtholnaphthalene — the constant tension was attributed
by Troost and Hautefeuille to the formation of a compound
Pd2H, in which any excess of hydrogen was then absorbed.
Quite recently, however, grave doubts have been thrown
on the existence of this compound. A very careful repetition
and extension of Troost and Hautefeuille's experiments by C.
Hoitsema has proved that the constancy of tension observed
by these investigators was not absolute but only approxi-
mate, and that under slightly varying conditions the
apparent constancy disappeared altogether. It would
seem, therefore, that no compound of palladium and hydro-
gen is formed when the gas is absorbed by the solid, the
state of the hydrogen being rather one of simple solution
in the palladium. A comparison of the concentrations of
the hydrogen above the palladium and of the hydrogen in
the palladium indicates that at very low pressures the
hydrogen in the metal exists as molecules only half as great
as those of the gas, i.e., as molecules consisting of only one
atom. At higher pressures the concentration of the free
gas and that in the palladium stand in a nearly constant
ratio, from which it is to be inferred that the molecule of
hydrogen in the metal, as well as the molecule of gaseous
hydrogen, is represented by the formula H2.

A problem which has long interested chemists is the
determination of the nature of the process involved in dyeing.
Some contended that the process was one of chemical union of
the dye with the substance of the fibre, others that it was
merely one of mechanical absorption. In 1890, however,
O. N. Witt propounded a new theory which, on account of

SOLID SOLUTIONS. 131

its plausibility, met with a ready acceptance in many
quarters.

According to Witt the state of the dye-stuff in the fibre
is one of solid solution, and many analogies were advanced
in support of this assertion. For example, dyed materials
show the colour, not of the solid dye-stuff, but of the dye-
stuff in solution, when there is a difference of colour between
the two states. Solid fuchsine is green, its aqueous solutions
are red, and so also are materials dyed with it. The dye-
stuff rhodamine in the solid state exhibits no fluorescence, in
solution it does, and silk dyed with rhodamine is fluorescent
likewise. The theory of Witt thus appeared very promising
as an explanation of the phenomena of dyeing, but a closer
investigation has shown that it cannot be accepted uncondi-
tionally, although some modification of it may be found to
satisfy the experimental requirements. It has been proved
in a considerable number of instances now investigated
that the concentrations of the dye in the dye-bath and
in the fibre do not stand to each other in a relation
of simple proportionality, but the concentration in the bath
is roughly proportional to a power (usually 3 to 5) of the
concentration in the fibre. Now on the theory of solid
solutions this indicates that the molecule of the dye in the
water is three to five times as great as the molecule of the
dye in the silk ; but this cannot be the case, for the mole-
cule of the dye-stuff in aqueous solution can be shown by
other means to be the simplest possible. The numbers
rather indicate analogy to the process known as absorption
from solution. Substances like animal charcoal and
platinum black have the property of condensing gases in
the extensive surface they present. Similarly they can
abstract certain substances from solution, as may be seen in
the employment of animal charcoal for the decoloration of
solutions. The relation between the concentration in the
solution and that in the charcoal proves to be of the same
kind as is met with in dyeing, so that we are led to suspect
a similarity in the nature of the two processes. The so-
called "iodide of starch," the blue compound formed when
starch and iodine solution are brought into contact, would

i32 SCIENCE PROGRESS.

appear to be a substance of the same nature as a dyed fibre
and as charcoal saturated with an acid from solution, for the
concentrations of the iodine in the aqueous solution and in
the starch obey approximately the same law as in the other
instances.

We are therefore forced to conclude that whatever
success has attended the application of the theory of
solid solutions to other processes, the theory can scarcely
without modification be accepted as giving an explanation
of the process of dyeing.

BIBLIOGRAPHY.

J. H. VAN'T Hoff. Zeitschrift fiir physikalische Chemie, v., 322

(1890).
A. VAN BlJLERT. Ibid., viii., 343 (1891).
O. N. WlTT. Fdrber-Zeitung, i. (1 890-91).
C. T. HEYCOCK and F. H. Neville. Journal of the Chemical

Society, Ixi., 888 (1892).

E. A. Schneider. Zeitschrift fiir physikalische Chemie, x., 425

(1893).
A. Ferratini and F. GARELLI. Gazzetta chimica italiana, xxii.,

ii., 245 ; xxiii., i., 442 (1893).

F. GARELLI. Ibid., xxiii., ii., 354 (1893).

F. GARELLI. Zeitschrift fiir physikalische Chemie, xviii., 51 (1895).
F. W. KtJSTER. Ibid., xii., 508 (1893); xiii., 445 (1894) 5 xv»-> 357
(1895).

F. W. KtJSTER. Liebigs Annalen, cclxxxiii., 360 (1894).

C. HoiTSEMA. Zeitschrift fiir physikalische Chemie, xvii., 1
(1895).

G. C. Schmidt. Ibid., xv., 56 (1894).

E. Beckmann and A. Stock. Ibid., xvii., 120 (1895).
J. M. VAN BEMMELEN. Ibid., xviii., 331 (1895).
G. V. GEORGEVICS. Monatshefte fiir Chemie, xv., 705 (1894).
G. v. Georgevics and E. Lowy. Ibid., xvi., 345 (1895).

James Walker.

THE STELAR THEORY; A HISTORY AND A

CRITICISM.

PART I.

IN the study of the histological anatomy of plants, apart
from the structure of the individual cell, the greatest
advances of the last two decades have been made rather by
the establishment of new points of view than by the dis-
covery of new facts. Twenty years ago the solid founda-
tions of the subject had been securely laid, and a consider-
able portion of the imposing fabric of histological detail
which now rests upon them had already been built up.
This fact is most clearly brought out by the masterly
summary of existing anatomical knowledge published by
De Bary in 1877. But splendid monument as it is of its
author's unsurpassed knowledge of his subject, there can be
few who have not felt that the Vergleichende Anatomie
is, as a whole, essentially unreadable. Compare it, in
imagination, with Sachs' Vorlesungen or with Haber-
landt's Physiologische Pflaiizenanatomie , and we are
forced to recognise that De Bary's work is rather an ency-
clopaedia than a piece of great scientific literature. The
cause is to be found in the simple fact that there did
not exist in 1877 a philosophy of the morphological aspect of
the subject capable of informing " an epitome of the pre-
sent knowledge of 'the Anatomy of the Vegetative Organs
of Vascular Plants,' " as the idea of adaptation informed the
works of Sachs and Haberlandt.

It is nothing less than the establishment of such a
philosophy that we now owe to the great Frenchman, Van
Tieghem. The most important part of his ideas is con-
tained in what we may call the Stelar Doctrine of Vascular
Tissue, and it is with this that we shall here be exclusively
concerned.

Although the foundations of the stelar theory were laid
many years ago, outside France it has made its way very
slowly. In Germany even now it is apparently ignored

134 SCIENCE PROGRESS.

by the majority of anatomists, notwithstanding its accept-
ance by the most brilliant of German contemporary in-
vestigators.

In England, though these ideas have recently been
made familiar to the student by more than one of our lead-
ing botanists, their discussion has still the interest of com-
parative novelty. And although the general idea of the
stele as a morphological unit is simplicity itself, yet the
application of this idea is in some cases by no means easy,
so that not only does Strasburger's interpretation of certain
facts differ from Van Tieghem's, but the author of the
theory has himself been led to modify his original views in
an important manner. The possibility of such a difference
in the interpretation of facts which are undisputed seems to
spring, if we may say so without presumption, from a
certain want of definiteness in the apprehension of the
criteria legitimate to their interpretation.

To investigate these criteria and to endeavour to as-
certain their relative validity is one of the primary objects
of the present paper.

We shall begin with an account of the development of
the stelar doctrine.

HISTORY OF THE STELAR DOCTRINE. FIRST PHASE—
THE IDEA OF THE CENTRAL CYLINDER.

In 1 8 70- 1, Van Tieghem published, in the Annales des
Sciences Nattirelles, a memoir (1) which was to have been
the first of a series entitled " Recherches sur la syme.trie
de structure des plantes vasculaires". This instalment con-
sisted of a general introduction setting forth the plan of
the whole work, followed by 274 pages devoted to an ex-
tended anatomical account of the root, in vascular plants.

The introduction is of the Greatest interest. The
author tells us how he wished to obtain anatomical defini-
tions of root, stem, and leaf, in order to give a basis to the
study of comparative anatomy. These definitions are to
be framed in accordance with the different kinds of sym-
metry exhibited in the arrangement of the vascular strands
in the three organs, to each of which a separate memoir

THE STELA R THEORY. 135

is to be devoted. The results so obtained are to be
applied, in a further series of memoirs, to the solution
of a number of morphological problems, such as the true
nature of tendrils, tubers, spines, phylloclades, ovules, etc.,
and finally, to the elucidation of the laws of symmetry
governing the structure and relations of the ideal colony
that would be formed if every seed germinated in situ.

This elaborate scheme for "un cercle d'etudes an-
atomiques complets et fermes " enables us to understand
the strength and the weakness of the author's stelar theory.
The imperative desire to reduce the anatomy of vascular
plants to a perfect system depending upon simple laws of
symmetry governing the arrangement of the vascular tissue,
has been the means of giving us a doctrine, luminous indeed,
and of wide significance, but scarcely of that rigidly uni-
versal application which its author claims. But here again,
as is so often the case in the history of science, the attempt
to work out logically the various implications of such a
theory, has been of the utmost value in clearing our ideas
and extending knowledge, not only by stimulating to the
discovery of new facts, but by forcing us to examine the
foundation of our conceptions.

Of Van Tieghem's scheme, as it stood in 1870, how-
ever, only the first memoir, that on the root, was ever
written. The author demonstrates the fundamental identity
of structure in the roots of all vascular plants, and obtains his
anatomical definition based on the symmetry of the vascular
system. He shows that the vascular tissue of a young root
forms a central cylinder which contains near its periphery
" faisceaux liberiens" (phloems) alternating with "faisceaux
vasculaires" (xylems) united by "cellules conjonctives ".
Hence the vascular system is symmetrical in relation to a
line, which is the organic axis of the organ. The stem
agrees with the root in this last point, but on the other
hand has its "faisceaux libero-vasculaires," " reunis directe-
ment par le parenchyme primordial ". Where the main
root passes into the main stem there occurs a "cessation du
tissu conjonctif special, qui se trouve remplace par le
parenchyme primitif ". This sentence is specially interest-

136 SCIENCE PROGRESS.

ing because it shows that when it was written Van Tieghem
had no idea of a central cylinder in the stem.

Two years later, however, in 1872, in describing (2)
the transition from root to shoot in Tagetes patiila, he
writes how the " membrane protectrice " (endodermis) is
continued up into the stem, retaining its characteristic
thickenings, and immediately internal to it the "membrane
rhizogene" of the root (later named the pericycle) is also
found in the stem still giving rise to rows of lateral roots,
one row arising from each interval between two bundles.
Opposite the bundles, however, he holds that the "membrane
rhizogene" is interrupted, since here the endodermis abuts
directly on the group of fibres capping the bundle, fibres
which in accordance with the current opinion he considered
to belong to the phloem. Here then we have the first
clear description of the continuation of the central cylinder
of the root into the stem, and the idea of this continuation
is the fundamental idea of the stelar theory. It is most
clearly expressed in a note on p. 112, " Ainsi, et j'insiste
sur ce point, la tige est, comme la racine, et dans toute son
etendue, composee d'un cylindre central et d'un parenchyme
cortical limite en dehors par un epiderme, en dedans par
une membrane protectrice ou endoderme ".

The generality of this condition is further insisted upon :
" Le caractere sur lequel je viens d'appeler l'attention se
retrouve dans la tige de la grande majorite des plantes
vasculaires, mais il souffre pourtant quelques exceptions.
M. Caspary a montre, en effet, que dans quelques plantes
(Minyanthes trifoliata, Adoxa moschatellina, Bi-asema
peltatd) chaque faisceau constitutif de la tige est indivi-
duellement entoure par une membrane protectrice a cellules
plissees (' Bemerkungen liber die Schutzscheide,' in Pring-
scheims Jahrbucher, 1865-66, iv., p. 10 1). J'ai retrouve le
meme fait sur quelques autres plantes, notamment sur
r Hydrocleis Humboldtii. Dans ce cas, il n'y a pas non
plus de membrane rhizogene dans les entrenceuds de la
tige, et il n'existe aucune solution de continuity aucune
distinction reelle entre le parenchyme cortical et la moelle '
(p. 113). This paragraph shows clearly that thus early

THE STELA R THEORY. 137

Van Tieghem had recognised the condition which he
afterwards described as " astely ".

The "membrane rhizogene," now considered, under the
name of pericycle, as forming merely the external layer of
the conjunctive tissue of the cylinder, was at that time
treated as a region external to, and distinct from, the rest
of the parenchyma, to which the name " conjonctif " was
given. But the clear recognition of the existence of an
individualised stem cylinder, forming a direct continuation,
tissue for tissue of that of the root, was the first and funda-
mental step in the evolution of the stelar idea.

Little progress was made during the next ten years in
the development of this conception.

Falkenberg (3), in 1876, showed that the " Aussen-
scheide " in monocotyledonous rhizomes corresponds with
the " pericambium " in roots, both in position and role ;
and Mangin (4) in 1882 entirely confirmed his results and
showed that not only adventitious roots but also the
" reseau radicifere " arises from this layer, which he calls
the " couche dictyogene ".

In 1882 Van Tieghem published a short paper (5) in
which, a propos of the Cucurbitacese, he gives conclusive
reasons, based upon grounds of comparative anatomy, for
regarding the fibres in the stem, hitherto called primary
"bast fibres," as really belonging to the "membrane
rhizogene ". With these extended limits, this layer forms a
complete investment of the stem cylinder, just as the peri-
cambium does of the root cylinder. Since the one layer is
the direct continuation of the other, and the two correspond
very largely in function as well as in position, it is clearly
desirable that they should have a common name. For this
purpose Van Tieghem introduced the word pericycle, which
was to supersede the various terms "pericambium,"
" Aussenscheide," "membrane rhizogene," "couche dictyo-
gene," etc., applied by various writers to the same layer in
various plants and parts of plants, according to its various
histological characters and functions. The importance of
this introduction of the conception of the pericycle was of
course very great, since it fixes more accurately the external

138 SCIENCE PROGRESS.

limit of the cylinder, and thus brings into greater promi-
nence the idea, already clearly stated in 1872, of an indi-
vidualised stem cylinder in direct continuity with that of
the root.

The term has eventually, though very slowly, found
its way into general use.

In 1884 Morot, a pupil of Van Tieghem, published the
results of a research (6) devoted to a comparative investiga-
tion of the pericycle in both root and shoot.

The publication of Morot's paper brings to an end what
we may call the first phase in the development of the stelar
idea.

SECOND PHASE— POLYSTELY AND ASTELY.

The second phase was inaugurated in an investigation (70)
by Van Tieghem and his pupil Douliot, of the anatomy of the
stem of various species belonging to the genus Primula. Their
observations were carried out on a number of new species from
the East, as well as on many old species, making together a
total of 114. They resulted [yd) in a division of the aggre-
gate genus Primula L., into two segregates, Primula Tourn.
and Auricula Tourn., as had been already done by Tourne-
fort, but now based on a fundamental difference in the
structure of the stem of the two segregate genera. While
the stem of the species belonging to Primula possesses
a single normal central cylinder in its whole extent, the
narrow cylinder of the hypocotyl of an Auricula, instead
of dilating in the ordinary way above the level of the coty-
ledons, gives rise by successive bifurcations to two or more
vascular strands, each surrounded by an endodermis and
possessing" the structure of the single hypocotyledonary
cylinder. In the genus Gunnera {Haloragece) a similar
state of things obtains. These facts were, in the main,
already known, having been investigated by Vaupell,
Kamienski and Reinke. The opinion of these authors
was, however, that the separate vascular strands were vas-
cular bundles of the " concentric " type with peripheral
phloem, comparable for instance to those found in the
cortex of certain Mclastoniace<z ; and this was the view

THE STELA R THEORY. 139

taken by De Bary in his classical Vergleichende Anatotnie.
The numerous vascular strands in the rhizomes of most
Leptosporangiate Ferns were regarded by De Bary in the
same light.

But Van Tieghem, having, as we have seen, come
to regard the central cylinder rather than the bundle as
the morphological unit of vascular tissue in both root and
shoot, was now led to the conclusion that in Auricula,
Gunnera and the majority of Ferns 1 we have really to
deal with a splitting- of the single cylinder of the hypocotyl,
as we trace it upwards, by successive bifurcations, into a
number of such cylinders (jc and 8). Van Tieghem
and Douliot proposed to call such a cylinder a stele (Greek
<7r/;X»7, a column). A root or a stem containing one such
stele would be monostelic, if it contained more than one
polystelic. A third case was distinguished. If the cylinder
of the hypocotyl breaks up, as it is traced upwards, into
its component bundles, each of which is surrounded by a
special endodermis, the cylinder, according to our authors,
no longer exists ; the stem is astelic. This case, already
described in 1872, obtains in the stems of various Ranun-
culacece, in Nymphceacece, in Hydrocleis, in some species of
Equisetum, etc., as well as in the majority of petioles and in
blades of all leaves.

Cases of Polystely fall into two groups. First, where
on a transverse section the various steles are seen to be
completely separate, we have a state of dialystely. Secondly,
where the steles are united laterally, so as to form a more or
less complete ring in transverse section, enclosing a more or
less isolated portion of extra-stelar tissue, which occupies the
centre of the ring, we have a state of gamostely. These
two conditions are not to be sharply separated, since the
steles of all polystelic stems show more or less frequent
lateral unions, and the gamostelic condition is simply a
case where these unions are very frequent and persistent.

1 Leclerc du Sablon in 1890 (9) worked out the connections, in
several Ferns, of the single hypocotyledonary cylinder with the cylinders
of stem.

140 SCIENCE PROGRESS.

We may tabulate the results thus obtained as follows: —

Monostely. — A single central cylinder. All roots and
hypocotyls, nearly all Phanerogamic stems, and stems of
many Vascular Cryptogams.

Polystely. — More than one cylinder. Stems of most
ferns, most species of Selaginella, and among Phanerogams
of Auricula and Gunner a}

(a) Dialystely.— Steles separate for most of their
course. Most Ferns Selaginella and. Auricula ursi, etc.
Gunnera.

(6) Gamostely. — Steles united laterally for most of their
course. Marsilia, Pilularia, Pteris aurita, etc. Auri-
cula japonica, etc.

Astely. — No cylinder. Leaf blades, most petioles,
stems of some species of Equisetum and Ranunculus^
stems of Hydrocleis, Ophioglossum, Limnanthonum, Nym-
phceacece, etc. (yc).

The publication, in 1890-91, of the second edition of
Van Tieghem's Trait e" de Botanique (10), which contains a
full exposition of the stelar doctrine on the lines indicated,
may be said to mark the close of the second phase in the
development of the theory.

THIRD PHASE— EXTENSIONS AND MODIFICATIONS.

The third phase, from that date to the present time, has
been occupied by various developments and modifications of
the doctrine on the part of the author and his pupils, and has
been marked by considerable criticism, mainly of these
newer developments.

The first line of research that calls for notice is a re-
investigation of the conjunctive tissue of the typical central
cylinder of the flowering plant. This has led Flot (11) to

1 In a paper recently communicated to the Linnean Society, Mr. B.
G. Cormack describes cases of polystely met with in the adventitious roots
of three genera of Palms, viz., Areca, Cocos and Verschaffeltia. It appears
that the single stele of the root splits, as it is traced downwards, into a ring
of separate steles. Later on these steles again pass over into a single
cylinder. This seems to be an important modification of Polystely as
described by Van Tieghem and Douliot, and Leclerc du Sablon.

THE STELA R THEORY. 141

add a new region to those already distinguished. He
finds a zone situated at the periphery of the pith, i.e., just
internal to the ring of bundles, corresponding exactly to
the pericycle external to the ring, as well characterised
histologically as the pericycle itself, and indeed resembling
the latter very closely in structure and role. This zone,
the perimedullary zone, is according to Flot (and his
figures entirely support this) separate in development from
the pith proper, or internal conjunctive, and belongs rather
to the hollow cylinder of tissue (the "thickening ring " of the
older German anatomists) giving rise to the bundles and
the conjunctive immediately surrounding them {external
conjunctive). It is impossible sharply to separate the peri-
medullary zone on the one side, just as Morot found it
impossible to separate the pericycle on the other, from the
ray tissue, and we should rather regard the contrast of
the pith with the external conjunctive tissue, as of greater
importance than the division of the latter into pericycle,
rays and perimedullary zone, which are in the main
topographical regions marked out by the limits of the
bundles. In many adult stems it is however impossible to
fix the limits of external and internal conjunctive, just as
it is often impossible to fix the limits between external con-
junctive and cortex. Flot is of opinion that this is owing
to a growth in breadth of the cells of the external conjunc-
tive continued longer than in the pith, the whole of the tissue
of the cylinder thus becoming approximated in size and
shape. This same cause, together with a masking of the
endodermal thickenings (in cases where these are originally
present) by a general thickening of the walls of all the
parenchyma cells may very conceivably account for the
frequent absence of the obvious limit between cortex and
cylinder, though we are not aware that such an occurrence
has been either established or suggested.1 Further in-
vestigation on this point, as well as on the separation of
the regions in root cylinders with a well-developed con-

XI now find that Sanio (24, pp. 371-2) states that this is practically
what occurs in the stem of Ranunculus acris.

i42 SCIENCE PROGRESS.

junctive system, is much needed to complete our know-
ledge of these matters.

An important modification of the theory of steles has
been made by Van Tieghem himself in extending the use
of the term astely so as to make it include the state of
things obtaining in the stems of all species of Equisetum
(12), and of 0 p hio gloss ace ce (13).

Let us take first the case of Equisetum. Well-
marked endodermes are found in the stems of all species,
but their disposition, which was fully worked out many
years ago by Pfitzer, is very various, not only in different
species, but in different parts of the stem of the same
species. There are three types of arrangement. In the
first each vascular bundle is surrounded by a special endo-
dermis ; in the second the ring of bundles is bordered within
and without by a general endodermis ; and in the third
the outer endodermis alone is present. In the second
edition of the Traite Van Tieghem assigned the first
two conditions to the astelic, the third to the monostelic
type, but in a paper (12) published in the same year (1890)
he calls attention to the fact, discovered by Pfitzer, that
all the species possess, at their nodes, the first or second of
the arrangements in question. He therefore concludes
that all belong really to the astelic type, and that where,
for instance, the second type, just above a node, passes
back into the third, we have simply a case of the dis-
appearance of the special characters of the inner endo-
dermis, which must still be supposed to exist. The " mono-
stely" is only apparent, and the tissue bordering the
central canal of the stem, internal to the inner (theo-
retical) "endodermis," is not in reality pith, but rather
" inner cortex" (extra-stelar tissue). The first of the three
arrangements is to be called dialydesmic, since each bundle
with its sheath of conjunctive is separate ; the second and
third gamodesmic, since the conjunctive tissue surrounding
the bundles is in lateral confluence.

Turning now to the Ophioglossacece we have a similar
argument (13). The stem of Ophioglossum vulgahtm,
below the level of the first leaf, is monostelic, but above the

THE STELA R THEORY. 143

first leaf contains five separate bundles each with a separate,
though feebly suberised, endodermis. Hence it was
treated by Van Tieghem, in the Traits, as astelic. In
Botrychium Lunaria, whose stem is also monostelic at the
base, the endodermis, after the departure of the first leaf
trace, does not close round each separate bundle but
becomes as it were invaginated into the cylinder, so that
the vascular tissue forms on transverse section a horse-
shoe bounded by the endodermis. The free edges of the
horseshoe meet, as we pass up the stem, and the inner
portion of the endodermis becomes entirely separated from
the outer, so that we have an equivalent of the second or
gamodesmic condition found in the stems of Eqtiiseta.
Higher up the inner endodermis loses its thickenings, just
as in some Equiseta, and this gives us an apparently
monostelic condition. In accordance with his revised
view, Van Tieghem considers that OpJiioglossum has an
astelic-dialydesmic stem, while those of Botrychium and
Helminthostachys are astelic-gamodesmic.

THE STATUS OF THE STELE CRITICISM.

It will be most convenient to introduce here a critical
investigation of the stelar theory as thus modified by its
author, and so far as it depends upon the morphological
interpretation of the arrangement and relations of vascular
tissue in the adult organs of vascular plants ; deferring for
the present a consideration of the developmental facts
bearing upon the theory.

There is no need to discuss at any length the funda-
mental conception of the stele arrived at in the period which
we have called the first phase of development of the idea.
It depends upon the tracing into the stem of the root
cylinder, and upon the demonstration that its characters as
a cylinder are maintained in the latter. This demonstration,
begun, as we have seen, in 1872, eventually led to the
explicit recognition of the fact that the system of bundles
forming the central cylinder possesses morphological charac-
ters much more constant than those of the vascular bundle,

144 SCIENCE PROGRESS.

and is hence more worthy to be taken as the morphological
unit of vascular tissue. It is indeed impossible to give a
morphological definition of a vascular bundle at all. " From
the very first those bundles which consist essentially of
definitely arranged groups of tracheae and sieve tubes . . .
have been called vascular bundles" (14, p. 232, Eng. ed.).
But thus defined, a "vascular bundle" has no constant
histological characters beyond the fact of containing both
xylem and phloem. According to the arrangement of these,
bundles have been classified as radial, concentric, collateral,
etc. Such an arrangement brings together vascular strands
of very different orders of complexity. In the first place
it associates the axial cylinder ("radial bundle") of a root,
possessing a number of quite distinct xylem and phloem
strands, with the "collateral bundle" of a Phanerogamic
stem, formed of a single strand of xylem and phloem in close
association, the latter being continuous moreover with a
portion only of the former. Again it associates even more
closely under the term " concentric bundle " the vascular
strands found in the stem of Auricula, Gunnera and Ferns
with those of quite different structure found in the pith and
cortex of Melastomacecz, etc.

Such a classification is clearly, from a morphological point
of view, quite artificial. But if we extend the use of the term
bundle, as is often done, so as to include strands of tracheae
alone, and of sieve tubes alone, we can retain it as a con-
venient word without morphological connotation, and
applicable to any strand of tissue belonging to the vascular
system. And we may then qualify the word by any adjec-
tive we choose without morphological implication. Thus we
may speak of the composite radial bundle of the root as
composed of separate xylem bundles and phloem bundles
alternating at its periphery ; of the concentric bundle of the
stem of an aquatic plant as sometimes composed of separate
collateral bundles, in other cases consisting simply of a con-
tinuous cylinder of phloem surrounding a central strand of
xylem ; of the concentric bundle of a fern petiole gradually
passing to the collateral type as we trace it into the lamina,
and so on. Meanwhile the study of the homologies of the

THE STELA R THEORY. 145

various strands is quite a distinct matter, and requires a
distinct terminology.

THE BOUNDARY OF THE STELE.

The acceptance of the central cylinder in the " mono-
stelic " stem as a region of the first morphological rank is
now very general. The only criticism which we have to
consider is that which calls attention to the frequent want
of definiteness about its external limit, and is inclined on
this ground to question its individuality. This want of
definiteness arises from the absence, in many adult stems,
of the special characters of the endodermis (innermost
layer of the cortex), often combined with an identity in
size, shape and characters of cell-membrane between
the cells of the cortex and those of the conjunctive. Such
a state of things obtains, to take a single instance, in the
stem of Ranunculus repens. A transverse section of such
a stem shows the separate bundles imbedded in a homo-
geneous ground tissue, and to speak of a well-marked central
cylinder is to speak of that which does not, in fact, exist.

Now this, as it stands, is a perfectly legitimate criticism,

and its force as against the general validity of the stelar

idea depends simply upon the greater or less generality of

the condition described. Van Tieghem (10, p. 752) states

that when, after the formation of the endodermis, the stem

undergoes considerable intercalary growth, the folds on

the radial walls of the endodermal cells become stretched out

so that they become difficult or impossible to see. In other

cases no suberisation of the radial walls occurs, and then,

unless the endodermal cells are distinguished by possessing

starch, it is admitted that the limit of the cylinder is difficult

to determine, but says Van Tieghem {Joe. eit.) : " il reste la

forme differente des cellules ". This, however, as has been

said, is by no means always obvious. A possible cause of

such a condition, assuming the limits of the young cylinder

to be well defined, has already been suggested, but

new investigations are necessary to determine the point.

If, for the sake of argument, we make the opposite assump-

10

146 SCIENCE PROGRESS.

tion, that the vascular bundles are sometimes differentiated
in the middle of a homogeneous ground tissue, no trace
of a special endodermis or pericycle being visible at any
time, we could not predicate the existence, in such cases,
of a central cylinder in the stem. And further, if such
a condition obtained in the majority of instances (certainly
an unlikely supposition) we should not, of course, be
justified in predicating the general existence in the stem
of a central cylinder, and this would necessitate such a
radical modification in the generalised statement of the
facts, that the stelar idea would lose the greater part of
its significance. We shall have to recur to a discussion
of the limit of the cylinder, but these simple considera-
tions are insisted upon here, because they are apparently
lost sight of in much of the current writing of Van Tieg-
hem's adherents. It seems to be implicitly assumed that if
a good anatomical distinction can be made in a certain
number of cases, it is permissible to generalise the distinc-
tion and erect it into a morphological doctrine. The
existence of those cases to which the doctrine does not
apply is either ignored, or the distinction is said to be
" theoretical ". There is of course no such thing as a true
"theoretical" distinction which is not also actual. The
fallacy arises from a tendency to regard all morphological
doctrine as of absolute value, whereas its value is never
anything but relative. What we have to decide in any
given case is the amount of this relative value, and whether
that amount is sufficient to make the doctrine express a
general truth so far as the objects under consideration are
concerned.

The foregoing reflections lead us naturally to consider
those cases which Van Tieghem himself excepts from the
application of the stelar doctrine, namely, the cases of
"astely". Already in the earliest paper containing the
germ of the stelar idea we find certain cases not covered
by the general statement of the existence of a cylinder in
the stem. In 1886 these cases together with other similar
ones were called astelic, and more recently still the concep-
tion has been further elaborated.

THE STELA R THEORY. 147

The conception is governed throughout by the idea of
the endodermis as a definite morphological layer, always
separating" stelar from extra-stelar tissue. And the en-
dodermis is to be recognised by the suberised thicken-
ings on its radial walls. It is simply by the disposition of
layers of cells so thickened that we are supposed to be
able to distinguish the various arrangements described.
It is easy to show that this criterion is quite illegitimate.
The term endodermis is defined by Van Tieghem as the
innermost layer of the cortex which " offre frequemment "
the special character in question (10, pp. 738-9). Not
only, however, do cell layers with the same character
occur in quite other situations {e.g., in the middle of many
periderms), but the innermost layer of the cortex certainly
does not always possess it. So that these thickenings
cannot be used to mark a layer of invariable morpho-
logical value. And even in Equisetum, Van Tieghem does
not keep to his own criterion. For when the " astelic
gamodesmic " passes to the apparently monostelic con-
dition we are told that the inner endodermis is still
present though its special characters have disappeared.
But, we may well ask, if such great importance is to be
attached to these special characters as to justify us in
founding new types of structure simply upon the disposition
of the layers exhibiting them, why should we be suddenly
asked to recognise as equivalent a layer which does not
exhibit them ? The criterion becomes completely chimeri-
cal.

Strasburger (15) has pointed out that an endodermoid
layer is an air-tight barrier which does not prevent the
passage of water through its cells. Such a layer is found
in a position to shut off the water-conducting system of a
plant from its air-containing lacunar system, but this posi-
tion may vary within the same genus [Ranunculus,
Equisetum), and has no necessary connection with any
morphological region. As a matter of fact it is most often
formed from the inner layer of the cortex, but may be
developed from conjunctive tissue, or even (leaf of Isoetes)
from intra-fascicular parenchyma. Since the innermost

148 SCIENCE PROGRESS.

layer of the cortex does not always possess the special
thickenings which give it the right to be called a
" membrane," Strasburger objects to Van Tieghem's re-
definition of the word endodermis, and proposes to sub-
stitute the term Phloeoterma, to be applied to the inner
layer of the cortex, i.e., to be used in the strictly morpho-
logical sense, whether this inner layer has special characters
or not, and to reserve the term endodermis in accordance
with its original sense for any sheath or membrane com-
posed of cells with suberised radial walls or other dis-
tinctive thickenings, without reference to its position.
This revised terminology certainly helps us to get rid
of the confusion of thought manifested in Van Tieg-
hem's use of the word endodermis. Strasburger concludes
that as all species of Equisetum agree in possessing a ring
of simple collateral bundles, they should all be considered
monostelic, whether the phloeoterma be developed as a
general endodermis, or each bundle possess a special
endodermis, the phloeoterma having no characters by which
it can be distinguished. The same considerations would
apply to the genus Ranunculus and the other cases of
"astely ". While we must fully admit the general force of
his argument on the ground of comparative anatomy, it is
difficult to agree with the following sentence : " Die
Grenze der Rinde gegen den Centralcylinder ist dort wo
sie sich nicht besonders als Endodermis oder Starkescheide
markirt, nur theoretisch zu ziehen, dieselbe ist aber flir alle
Falle festzuhalten ': (15, p. 484). How is one to "hold
fast " a limit which one cannot distinguish ? We can only
refer to the remarks which have been already made upon
this subject, but we shall briefly recur to the subject in
considering the development of the stele.

Leaves furnish us with excellent examples of the frequent
impossibility of separating stelar from extra-stelar tissue.
Putting aside those cases in which one or more steles
from the polystelic stem directly enter the petiole
[Gunncra, Ferns), we have to consider the ordinary
case in a flowering plant, where we have one or more
bundles leaving the cylinder and passing into the petiole.

THE STELA R THEORY. 149

These bundles are accompanied by a certain amount of
closely associated parenchyma belonging to the external
conjunctive of Flot, a tissue which in the leaf Van Tieghem
now calls peridesm (16). The bundles are sometimes
arranged in a ring, and the whole may be, though com-
paratively rarely, surrounded by an endodermis. The
petiole is then, according to Van Tieghem (10, p. 842),
monostelic. In the commoner case where each bundle has
an endodermis of its own the petiole is astelic.

Strasburger prefers the term schizostelic (15), since the
stelar tissue of the petiole represents a separated portion or
portions of that of the stem. To such a portion he gives the
name schizostele or schistostele \ at the same time denying the
existence of monostelic petioles in Phanerogams on the
ground that the apparent pith of the petiole is continuous
with the cortex, and not with the pith, of the stem. This
last contention brings forward a difficult position. Is it de-
sirable to introduce the question of continuity at all ? If we
have in the petiole a structure apparently identical with that
which we have agreed to call monostelic in the stem, should
we be satisfied to call it monostelic here also, without con-
sidering the connections of its parts with those of the stem ?
The strength of Strasburger's position lies in the fact that
the continuity, region for region, of the cylinder of root
and stem is really the basis of the stelar idea. The origin
of the difficulty is to be found in the tendency of a petiole,
where it is subject to the same conditions as a stem, to
assume the characters of a stem, and among them the
arrangement of its vascular tissue according to a radially
symmetrical type. We might, perhaps, fitly call such a
structure a pseudostele.

The mesophyll of the leaf (corresponding with the cortex
of the stem) which surrounds the smaller vascular bundles,
often has its innermost layer or phloeoterma, which abuts

1Van Tieghem has since (17, p. 285) used the word meristele for
Strasburger's " schizostele," and applied the latter term to the portion of
stelar tissue enclosed by each special endodermis in an "astelic" stem.
This seems an unwarrantable diversion of the meaning of Strasburger's
term.

i5o SCIENCE PROGRESS.

immediately upon the peridesm of the bundle, specially
characterised. The cells of the phloeoterma are often de-
prived of chlorophyll, or this is confined to the side walls,
and these walls may also be suberised. It is, however, a
rare case for such layers to be united in a continuous
system with the phloeoterma of the stem, and thus to shut
off completely, by means of a continuous membrane, the
entire stelar system of the plant from its cortical tissue.
This state of things obtains, however, in Pinus and some
dicotyledonous genera, e.g., Galium. In most dicotyledo-
nous petioles endodermoid layers, if distinguishable at all,
are often incomplete and not necessarily formed from the
phloeoterma. A closed sheath to the bundles is, however,
often formed in Angiosperm petioles by thickened peri-
desmic (stelar) tissue, such a sheath being called by Stras-
burger a stelolemma (15). The ensemble of the phenomena
shows us, clearly enough, that the endodermis, in its original
sense, cannot be taken here, any more than in the stem,
as a layer of constant morphological value. The phloeo-
terma may be distinguishable by endodermal or other char-
acters, but on the other hand, it may not.

The main fact in regard to the vascular system of the
leaf is one which was pointed out by Van Tieghem in 1870.
The system is bilaterally symmetrical in relation to the
plane including the organic axes of both leaf and stem,
and not, like that of root and stem, radially symmetrical
about its organic axis. The designation of the continuous
cylinder of root and stem as a stele and of each bundle or
the whole bundle system of the leaf as a schistostele or
meristele is in complete accord with this general fact. But
we must not disguise from ourselves that both the stele and
the meristele may not exist in the adult as sharply separated
structures.

A. G. Tansley.
( To be contimted. )

ON SOME APPLICATIONS OF THE THEORY
OF OSMOTIC PRESSURES TO PHYSIO-
LOGICAL PROBLEMS.

PART II.

IN my previous article I gave some account of a research
by Heidenhain in which this observer, after drawing
certain deductions from the theory of osmotic pressures, shows
that the phenomena of absorption from the intestinal canal are
irreconcilable with these deductions, and are therefore not
susceptible of a mechanical explanation, but must be as-
cribed to the active intervention of cells. Since analogous
problems to those discussed by Heidenhain are continually
coming before us in physiology, it is important that we
should have a clear idea of the factors which are involved
in the passage of water or dissolved substances across
membranes. I therefore propose to reproduce Heiden-
hain's statements, and then to consider how far they are
true for the special cases which occur in the body.

These statements are as follows : —

i. If two watery solutions with the same osmotic pres-
sure are separated by a membrane through which diffusion
can take place, no change in volume occurs on either side
of the membrane.

2. If the solutions on either side of the membrane are of
unequal osmotic pressure, water passes from the side where
the pressure is less to the side where the osmotic pressure
is greater.

3. The osmotic pressure of a solution is equal to the sum
of the partial pressures of the various dissolved substances.

4. If the solutions on the two sides of the membrane
have the same total osmotic pressure but unequal partial
pressures of their various constituents, each constituent of
the solution passes from the side where it has the higher
partial pressure to the other side. No change in the volume
of water on the two sides takes place.

Of these four statements only one (No. 3) is absolutely

152 SCIENCE PROGRESS.

correct. The other three are only correct under certain
defined conditions which are rarely fulfilled in the body.
There are factors at work which have been practically dis-
regarded by most of the recent workers on the subject, and
which may tend to produce movement of fluid in apparent
opposition to the difference of osmotic pressure. Instances
of such cases are afforded in a paper by Lazarus Barlow, to
a consideration of whose work we shall shortly return.

There can be no doubt that in the phenomena of trans-
ference of fluid or dissolved substances across a membrane
the nature of the membrane itself is all-important. I will,
therefore, shortly run through the various modes in which
interchanges may take place across membranes of varying
permeability. We shall see that the close analogy which
exists between substances in solution and gases, when
dealing with "semi-permeable" membranes, is also borne
out by experiment when used to predict the behaviour of
solutions separated by such permeable membranes as occur
in the body.

The simplest case is that in which two fluids are sepa-
rated by a perfect semi-permeable membrane that permits
the passage of water but is absolutely impermeable to dis-
solved substances. In this case the transference of water
from one side to the other depends entirely on the difference
of osmotic pressure between the two sides.

m.

A

B

If we suppose two vessels, A and B, separated by such
a membrane, A containing a solution of a and B a solution
of (5, water will pass from A to B so long as the osmotic
pressure of /3 is greater than the osmotic pressure of the
solution of a. If B be subjected to a hydrostatic pressure
greater than the osmotic difference between the two fluids,
water will pass from B to A until the force causing filtration
or transudation (the hydrostatic pressure) is equal to the

THE THEORY OF OSMOTIC PRESSURES. 153

force causing absorption into B (the difference of osmotic
pressures). Under no circumstance will there be any trans-
ference of salt or dissolved substance between the two sides.
Such semi-permeable membranes as this, however, rarely
occur in the body. It is possible that the external layer of
the cell-protoplasm may in some cases resemble the proto-
plasmic pellicle of plant-cells in possessing this "semi-per-
meability " ; but in nearly all cases where we have a mem-
brane made up of a number of cells, it can be shown that
such a membrane permits the free passage of at any rate a
large number of dissolved substances.

Let us now consider what will occur when the two solu-
tions A and B are separated by a membrane which permits the
free passage of salts and water. If the osmotic pressure of
B be higher than A at the commencement of the experi-
ment, the force tending to move water from A to B will be
equal to this osmotic difference. But there is at the same
time set up a diffusion of the dissolved substances from B
to A and from A to B. The result of this diffusion must
be that there is no longer a sudden drop of osmotic pressure
from B to A, and the result of the primary osmotic difference
on the movement of water will be minimised in proportion
to the freedom of diffusion which takes place through the
membrane. Now let us take a case in which A and B re-
present equimolecular and isotonic solutions of o and /3.
It is evident that the movement of water into A will vary
as Ap - Bpl = O. But diffusion also occurs of a into B and
of (3 into A. Now the amount of substance diffusing from
a solution is proportional to the concentration, and there-
fore to its osmotic pressure, as well as to its diffusion
coefficient.

Hence the amount of a diffusing into B will vary as
Aft . ak (when k is the diffusion coefficient).

In the same way the amount of (3 diffusing into A will
vary as Bp, (5k'.

Hence if ak is greater than (3k', i.e., if a is more diffusible
than (3, the initial result must be that a greater number of

1 Ap = osmotic pressure of A, etc.

154 SCIENCE PROGRESS.

molecules of o will pass into B than of /3 into A. Hence
the solutions on the two sides of the membrane will be no
longer equimolecular, but the total number of molecules of
a + (3 in B will be greater than the number of molecules of
a + j3 in A, and this difference will be most marked in the
layers of fluid nearest the membrane. The result therefore
of the unequal diffusion of the two substances is to upset
the previous equality of osmotic pressures. The layer of
fluid on the B side of the membrane will have an osmotic
pressure greater than the layer of fluid in immediate contact
with the A side of the membrane, and there will thus be a
movement of water from A to B. Hence if we have two
equimolecular and isotonic solutions of different substances
separated by a membrane permeable to the dissolved sub-
stances, there will be an initial movement of fluid towards
the side of the less diffusible substance.

We have an exact parallel to this in Graham's familiar
experiment in which a porous pot filled with hydrogen is
connected by a vertical tube with mercury. In consequence
of the more rapid diffusion outwards of the hydrogen than
of atmospheric air inwards, the pressure within the pot sinks
below that of the surrounding atmosphere, and the mercury
rises several inches in the tube. We must therefore con-
clude that even when the two solutions on either side of the
membrane are isotonic, there may be a movement of fluid
from one side to the other with a performance of work in
the process.

The experimental proof of the truth of this argument is
to be found in a recent paper by Dr. Lazarus Barlow.
This observer — after pointing out that the huge total
osmotic pressures of the salt solutions in the body can very
seldom come into play — insists on the fact that the most im-
portant point to study in this regard is the initial changes
that take place between dissimilar fluids separated by a
membrane — as he terms it — the initial rate of osmosis. For
this purpose he employs a funnel, the neck of which is pro-
longed into a capillary tube, while on the mouth is tied a
piece of peritoneal membrane. The funnel is filled with
the solution whose osmotic attraction for water it is wished

THE THEORY OF OSMOTIC PRESSURES. 155

to measure, and its mouth covered with the membrane is
immersed in distilled water or in dilute serum.

The experiments which are the most interesting are
those in which decinormal solutions of glucose, urea,
sodium chloride were compared as to their initial rates of
osmosis, the outer fluid being water. He concludes from
his experiments that, in the case of prepared peritoneal
membrane, the initial rates of osmosis of glucose, sodium
chloride and urea in equimolecular solutions do not corre-
spond to the ratio between their final osmotic pressures (as
estimated by the depression of freezing-point), but the
initial rate of osmosis of glucose {i.e., the rate with which
water passes into this solution) is greater than that of
sodium chloride, and the initial rate of osmosis of sodium
chloride greater than that of urea.

In these experiments the only two solutions which
are strictly comparable are those of urea and glucose
(A = 0*189° C), since the decinormal Na CI solution had
nearly double the osmotic pressure of these two (A = 0*35 1).
In three typical experiments, each of which lasted three
hours, the average rates at which the fluid in the funnel
increased in volume during the first hour were : in the case
of glucose, 7! mm. in five minutes ; in the case of sodium
chloride, 43 mm. ; and in the case of urea, iJT mm.
These figures are evidently not proportional to the differ-
ence of osmotic pressures between the fluid and the funnel
and the water in the reservoir. But we have already seen
that the moving force is not the total difference of pressure
between the fluids in the vessels on either side of the
membrane, but the difference of pressure between the
layers of fluid in immediate contact with each side of the
membrane. The fall of osmotic pressure across the thick-
ness of the membrane varies inversely as the rate of
diffusion of the dissolved substance. The question arises
therefore whether the results obtained by Lazarus Barlow
can be accounted for by differences in the rate of diffusion.
In the carefully worked-out tables by this observer we have
all the data necessary to decide the question. In the case
of glucose, the freezing-point of the solution at the begin-

156 SCIENCE PROGRESS.

ning of the experiment was - o'i8q° ; at the end of the three
hours' experiment it was — ot JJ° C. — corresponding to a
loss of 6 per cent, of the dextrose. In the case of the
urea, the freezing-point at the beginning was "189°, and at
the end was- 0*154° C, a loss of 18 per cent. Here then
the initial rate of osmosis of the glucose was about five
times that of the urea ; the loss by diffusion of the glucose
was about one-third that of the urea. In the case of the
sodium chloride the loss amounted to 22 per cent. ; but
here the total difference of osmotic pressure was very
nearly double that of the other two solutions, and the result
is that the initial rate of osmosis of the sodium chloride takes
an intermediate place between that of urea and that of
glucose.

In this paper the results of another experiment are
given to show that osmosis may occur from a fluid having
a higher final osmotic pressure towards a fluid having a
lower final osmotic pressure. If, for example, equimolecu-
lar solutions of sodium chloride and glucose be separated
by a peritoneal membrane, the osmotic flow will take place
from the fluid having the higher final osmotic pressure —
sodium chloride. We might compare with this experiment
the results of separating hydrogen at one atmosphere's
pressure from oxygen at two atmospheres' pressure by
means of a plate of graphite. In this case the initial result
will be a still further increase of pressure on the oxygen
side of the diaphragm — a movement of gas against pres-
sure taking place in consequence of the greater diffusion
velocity of hydrogen.

So far we have only considered the behaviour of solu-
tions when separated by a membrane, the permeability of
which to salts is comparable to that of water ; so that the
passage of salts through the membrane depends merely on
the diffusion rates of the salts. There can be no doubt,
however, that we might get analogous movements of fluid
against total osmotic pressure determined, not by the
diffusibility of the salts, but by the permeability of the mem-
brane for the salts — a permeability which may depend on a
state of solution or attraction existing between membrane

THE THEORY OF OSMOTIC PRESSURES. 157

and salts. We have a familiar analogue to such a condition
of things in the passage of gases through an india-rubber
sheet. If two bottles, one containing carbonic acid, the
other hydrogen, be separated by a sheet of india-rubber,
C03 passes into the hydrogen bottle more quickly than
hydrogen can pass out into the C02 bottle, so that a dif-
ference of pressure is created between the two bottles, and
the rubber bulges into the C02 bottle. We might, in the
same way, conceive of a membrane which permitted the
passage of dextrose more easily than that of urea. With
such a membrane, experiments conducted in the same way
as Dr. Barlow's, would lead to diametrically opposite re-
sults. The importance of the membrane in determining
the direction of the osmotic passage of fluid is well illustrated
by Raoult's experiments. When alcohol and ether were
separated by an animal membrane, alcohol passed into the
ether, whereas if vulcanite were employed for the dia-
phragm, the osmotic flow was in the reverse direction,
and an enormous pressure was set up on the alcohol side of
the diaphragm.

Here we have a possible clue to the "explanation" of
many phenomena of cell activity, to which the term " vital"
is often assigned. In the swimming-bladder of fishes, for
instance, we find a gas which is extremely rich in oxygen,
and the oxygen is said to have been secreted by the cells
lining the bladder. It is, however, very possible that the
processes here may be exactly analogous to Graham's
atmolysis, and that the bladder may represent a perfected
form of Graham's india-rubber bag.

The next point to be considered is the passage of a
dissolved substance across membranes in consequence of
differences in the partial pressure of the substance in ques-
tion on the two sides of the membrane. Great stress is
laid by Heidenhain and his pupil Orlow on the fact that
in the peritoneal cavity, as well as from the intestine, salt
may be taken up from fluids containing a smaller percentage
of this substance than does the blood plasma, and they
regard this absorption as pointing indubitably to an active
intervention of living cells in the process. This argument

158

SCIENCE PROGRESS.

requires examination. Supposing the two vessels A and B
to be separated by a membrane which offers free passage
to water, and a difficult passage to salts. Let A contain '5

n

A

B

per cent, salt solution and B a solution isotonic with a 1
per cent. Na CI, but containing only '65 per cent, of this
salt, the rest of its osmotic tension being due to other dis-
solved substances. If the membrane were absolutely " semi-
permeable," water would pass from A to B until the two
fluids were isotonic, i.e., until A contained 1 per cent. Na CI
(we may regard volume of B as infinitely great to
simplify the argument). If, however, the membrane per-
mitted passage of salt, the course of events might be as
follows : At first water would pass out of A, and salt would
diffuse in until the percentage of Na CI in A was equal
to that in B. There would now be an equal partial pres-
sure of Na CI on the two sides of the membrane, but the
total osmotic pressure of B would still be higher than A.
Water would therefore still continue to pass from A to B
more rapidly than the other ingredients of B could pass
into A. As soon, however, as more water passed only
from A, the percentage of N a CI in A would be raised
above that in B. The extent to which this occurs will
depend on the impermeability of the membrane. As soon,
however, as the Na CI in A reaches a certain concentration
it will pass over into B, and this will goon until equilibrium
is established between A and B. Extending this argument
to the conditions obtaining in the living body, we may con-
clude that neither the raising of the percentage of a salt
in any fluid above that of the same salt in the plasma, nor
the passage of a salt from a hypotonic fluid into the blood
plasma, can afford in itself any proof of an active interven-
tion of cells in the process.

THE THEORY OF OSMOTIC PRESSURES. 159

Thus in the case of the pleura we seem to have a mem-
brane which is very imperfectly semi-permeable. It is per-
meable to salts, but presents rather more resistance to their
passage than to the passage of water. Hence on injecting
•5 per cent. Na CI solution into the pleural cavity water
passes from the pleural fluid into the blood, until the per-
centage of sodium chloride in the fluid is raised perceptibly
above that in the blood plasma. The limit of the resistance
of the pleural membrane to the passage of salt is, however,
soon reached, and then salt passes from pleural fluid into
blood ; but in every case this passage is from a region of
higher to a region of lower partial pressure. Hence at
a certain stage of the experiment we find a higher percentage
of salt in the pleura than in the blood-vessels, although
the total amount of salt in the pleural fluid is less than
that originally put in, or, in other words, salt has been
absorbed.

We have already seen that the effective osmotic pressure
of a substance, i.e., its power of attracting water across a
membrane, varies inversely as its diffusibility, or as the
permeability of the membrane to it. What then will be
the effect supposing that on one side of the membrane we
place some substance in solution to which the membrane
is impermeable ?

We will suppose that A and B both contain 1 per cent.
Na CI, but that B contains in addition some substance x to
which the membrane is impermeable. Since the osmotic
pressure of B is higher, by the partial pressure of x, than
that of A, fluid will pass from A to B by osmosis. But the
consequence of this passage of water will be to concentrate
the Na CI in A, so that the partial pressure of this salt in
A is greater than in B. Na CI will therefore diffuse from
A to B with the result that the former difference of total
osmotic pressure will be re-established. Hence there will
be a continual passage of both water and salt from A to B,
until B has absorbed the whole of A. This result will
be only delayed if the osmotic pressure of A is at first
higher than B, in consequence of a greater concentration
of Na CI in A. There may be at first a flow of fluid

160 SCIENCE PROGRESS.

from B to A, but as soon as the Na CI concentration on
the two sides has become the same by diffusion the power
of x to attract water from the other side will make itself
felt, and this attraction will be proportional to the osmotic
pressure of x.

We have an example of such a process in the absorption
of salt solutions from the connective tissues by the blood-
vessels, as well as in the absorption of the normal tissue
lymph. The capillaries of the connective tissues of the
limbs and peripheral parts of the body are almost imperme-
able to proteids. In consequence of this impermeability the
fluid which is transuded from the capillaries under pressure
contains very little proteid, whereas it contains exactly the
same proportion of salts as does the blood plasma. It seems
probable therefore that the proteid left in solution in the
capillaries must exert a certain osmotic attraction on the
salt solution outside the capillaries. It is easy to
measure this attractive force. If blood serum be placed in
a small thistle funnel, on the open end of which is stretched
a layer of membrane soaked in gelatine, and the inverted
funnel be immersed into salt solution which is isotonic or
even hypertonic as compared with the serum, measured by
the freezing-point, within the next two to four days fluid
will pass into the funnel and rise up in its capillary stem to
a considerable height. I have found that the osmotic
pressure of the non-diffusible constituents of blood serum
measured in this way amounts to between 30 mm. and 40 mm.
Hg. Now although this osmotic pressure is so small, it is of an
order of magnitude comparable with that of the hydrostatic
pressure in the capillaries. This fact is of importance in
that, whereas the capillary pressure determines transudation
from the vessels, the effective osmotic pressure of the
serum (proteids ?) determines absorption by the blood-
vessels. Moreover the osmotic attraction of the serum for
the extravascular fluid will be proportional to the force
expended in the production of this extravascular fluid, so
that at any given time there must be a balance be-
tween the hydrostatic pressure in the capillaries and the
production or absorption of fluid from the extravascular

THE THEORY OF OSMOTIC PRESSURES. 161

spaces — a balance which is known to obtain under physio-
logical conditions. If we increase the volume of circulating
fluid we increase intracapillary pressure and the blood
volume tends to diminish in consequence of increased
transudation. If we diminish the capillary pressure by
bleeding the animal, absorption will predominate over exu-
dation, and the volume of circulating fluid will tend to
increase towards its normal amount.

From this cursory study of some of the simplest examples
of transference of fluids and salts across membranes, we
may draw certain conclusions as to the main factors which
are of importance for the process.

These are : (i) The permeability of the membrane to the
dissolved substances. This permeability may be of the
same character as the permeability of water, in which case
the rates of passage of the dissolved substances across the
membrane vary as their diffusibilities, and are therefore
probably some function of their molecular weights. On the
other hand the membrane may exhibit a certain attraction
for, or power of dissolving, some dissolved substances to the
exclusion of others, in which case there will be no relation
between the diffusibilities and rates of passage of the dis-
solved substances.

(2) The osmotic pressure of the solutions. It is evident
that the rules deduced by Heidenhain from the accepted
theory of osmotic pressures, and quoted at the beginning of
this article, are fallacious in consequence of a too narrow con-
sideration of this second factor to the exclusion of the first.
At the same time it must be confessed that our knowledge
of the permeability of different membranes to different
substances, as well as of the factors on which this per-
meability depends, is still in an embryonic condition.
There can be no doubt that a careful exploration of this
field of research would yield results not only interesting
to the physicist, but also of incalculable value to the
physiologist in his investigation of the phenomena of
living things.

11

162 SCIENCE PROGRESS.

BIBLIOGRAPHY.

(i) Heidenhain. Neue Versuche liber die Aufsaugung im Diinn-
darm. Pfiiigers Archiv, lvi., p. 600, 1894.

(2) LAZARUS BARLOW. Observations upon the Initial Rates of Os-

mosis of certain Substances in Water and in Fluids containing
Albumen. Journ. of Phys., vol. xix., p. 140, 1895.

(3) ORLOW. Einige Versuche iiber die Resorption in der Bauch-

hohle. Pfiiigers Archiv, vol. lix., p. 170, 1894.

(4) Leathes and Starling. On the Absorption of Salt Solutions

from the Pleural Cavities. Journ. of Phys., vol. xviii., 1895.

(5) Leathes. Some Experiments on the Exchange of Fluid be-

tween the Blood and Tissues. Journ. of Phys., vol. xix., p. 1,

1895.

(6) HAMBURGER. Ueber die Regelung der osmotischen Spannkraft

von Fliissigkeiten in Bauch und Pericardialhohle. Du Bois
Archiv, p. 281, 1895.

(7) STARLING. On the Absorption of Isotonic Solutions from the

Connective Tissues. Journ. of Phys., 1896.

Ernest H. Starling.

Science |)ragre$s.

No. 27. May, 1896. Vol. V.

THE PAST, PRESENT AND FUTURE WATER
SUPPLY OF LONDON.1

IN a discourse to the Members of the Royal Institution
on the subject of the Metropolitan Water Supply
nearly thirty years ago, I stated that out of every thousand
people existing upon this planet at that moment, three
lived in London ; and, as the population of London
has in the meantime doubtless grown at a more rapid rate
than that of the rest of the world, it will probably be no
exaggeration to say that now, out of every thousand people
alive on this earth, four live in London ; and therefore any
matter which immediately concerns the health and comfort
of this vast mass of humanity may well merit our most
earnest attention. Amongst such matters that of the
supply, in sufficient quantity, of palatable and wholesome
water is certainly not the least in importance.

It is not therefore surprising that this subject has
received much attention from several Royal Commissions, —
notably from the Royal Commission on Water Supply of
1867, presided over by the Duke of Richmond, the Royal
Commission on the Pollution of Rivers and Domestic
Water Supply of Great Britain, presided over by the late
Sir William Dennison, of which I had the honour to be a
member ; and lastly the Royal Commission, appointed in
1892 to inquire into the Water Supply of the Metropolis,

1 A discourse delivered at the Royal Institution, 21st February, 1896.

12

1 64 SCIENCE PROGRESS.

of which Lord Balfour of Burleigh was Chairman, and of
which Professor Dewar was a member.

The Royal Institution has also for nearly three-quarters
of a century been prominently connected with the investiga-
tion and improvement of the Metropolitan Water Supply ;
no less than four of our Professors of Chemistry having
been successively engaged in this work, viz., Professors
Brande, Odling, Dewar, and myself, whilst three of them
have been members of the Royal Commissions just
mentioned. I may therefore perhaps be excused for
accepting the invitation of our Secretary to bring the
subject under your notice for the third time.

On the present occasion I propose to consider it from
three points of view, viz., the past, the present and the
future ; and, for reasons which will appear hereafter, I shall
divide the past from the present at, or about, the year 1883,
and will not go back farther than the year 1828, when Dr.
Brande, Professor of Chemistry in the Royal Institution ;
Mr. Telford, the celebrated engineer ; and Dr. Roget,
Secretary of the Royal Society were appointed a Royal
Commission to inquire into the quality and salubrity of the
water supplied to the Metropolis.

The Commissioners made careful examinations and
analyses, and reported as follows : " We are of opinion that
the present state of the supply of water to the Metropolis
is susceptible of, and requires, improvement ; that many of
the complaints respecting the quality of the water are well
founded, and that it ought to be derived from other sources
than those now resorted to, and guarded by such restrict-
tions as shall at all times ensure its cleanliness and purity.
(At this time the water was pumped from the Thames
between London Bridge and Battersea.) To obtain an
effective supply of clear water free from insects and all
suspended matter, we have taken into consideration various
plans of filtering the river water through beds of sand and
other materials ; and considering this, on many accounts, as a
very important object, we are glad to find that it is perfectly
possible to filter the whole supply, and this within such
limits, in point of expense, as that no serious objection can

THE WATER SUPPLY OF LONDON. 165

be urged against the plan on[ that score ; and with such
rapidity as not to interfere with the regularity of service."

Before the year i82g, therefore, the river water supplied
to London was not filtered at all ; but after the issue of
this report, the Companies set themselves earnestly to work
to improve the quality of the water by filtration.

The first filter, on a working scale, was constructed and
brought into use by the Chelsea Water Company in the
year 1829. But even as late as 1850 only three out of the
seven principal companies filtered the river water which
they delivered in London ; and it was not until 1856 that
filtration was made compulsory by Act of Parliament,
whilst it can scarcely be doubted that, between this date and
the year 1868, when my observations on turbidity were first
commenced, the operation was very imperfectly performed.

In the year 1832, and again in 1849, London was
severely visited by epidemic cholera, and the agency of
drinking water in spreading the disease forced itself upon
the attention of the observant portion of the medical pro-
fession. It was Dr. Snowe, however, who in August,
1849, first formally enunciated the doctrine that drinking
water polluted by choleraic matters is the chief mode by
which cholera is propagated.

Received at first with incredulity, this doctrine was
supported by numerous facts, and it soon caused renewed
attention to be directed to the quality of the water then
being supplied to the Metropolis ; with the result that the
intakes of the various Companies drawing from rivers
were, one after another, removed to positions above the
reach of tidal influence ; the Thames water being with-
drawn from the river above Teddington Lock, and the Lea
water at Ponder's End, above the tidal reaches of that river.

In every visitation of Asiatic cholera to London, the
water supply was either altogether unfiltered or imperfectly
filtered, besides being derived from highly polluted parts
of the Thames and Lea ; and the enormous loss of life,
amounting in the aggregate to nearly 36,000 people, can
only be attributed to this cause. It has been abundantly
proved that efficient filtration is a perfect safeguard against

1 66 SCIENCE PROGRESS.

the propagation of the disease, and since the year 1854 no
case of Asiatic cholera in London has been traced to the
use of filtered river water.

These are the results arrived at by the most general
investigation of the subject. They show that in every
epidemic, the mortality varied directly with the intensity of
the drainage pollution of the water drunk by the people ;
but if time permitted, a more detailed study of the
statistics in both epidemics would demonstrate, much more
conclusively, this connection between cholera mortality and
the pollution of drinking water — a connection which has quite
recently been terribly emphasised in the case of Hamburg.

Such is the verdict with regard to cholera, and the
same is true of that other great water-borne disease typhoid
fever. But, unlike cholera, this disease is disseminated in
several other ways, and its presence or absence in any
locality may not, of necessity, have any connection with
drinking water, as is strikingly shown by the health
statistics of Manchester.

There is no evidence whatever that, since the year
1869, when typhoid fever appeared for the first time as a
separate disease in the Registrar General's reports, it has
been conveyed by the water supply of the Metropolis.
An inspection of the diagram (No. 1) shows, it is true, a
greater proportional mortality during the period of imperfect
filtration than during the later period ; that is to say from
1883 when the process began to be performed with uniform
efficiency ; but the plotting of a similar curve for the deaths
by typhoid in Manchester shows that this disease arises from
other causes than polluted water, since the water supply
of Manchester, derived as it is from mountain sources, is
above all suspicion of this kind. These other causes have
during the last ten years been much mitigated in London
by various sanitary improvements ; whilst, as shown in
the diagram, there has been no corresponding mitigation
in Manchester.

Although very soon after the year 1856 all the water
supplied to the Metropolis was obtained from sources much
less exposed to drainage pollution, it was still very carelessly

THE WATER SUPPLY OF LONDON.

167

filtered. Previous to the year 1868, there are no records
of the efficiency, or otherwise, of the filtration of the
Metropolitan water supply derived from rivers, as dis-
tinguished from deep wells, the water of which is perfectly
clear without filtration.

It was in the year 1868 that I first began to examine
the water supplied to the Metropolis from rivers with
reference to efficiency of filtration. I n that year, out of
eighty-four samples examined, seven were very turbid,
eight turbid, and ten slightly turbid, so that altogether no
less than nearly 30 per cent, of the samples were those of
inefficiently filtered water. The Metropolitan Water Supply
then, up to the year 1868, may be shortly described as

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derived for many years from very impure sources with
either no filtration at all, or with very inefficient filtration ;
and afterwards, when the very impure sources were
abandoned, the supply was still often delivered in a very
inefficiently filtered condition. But, after the establishment of
monthly reports on the filtration of the river-derived supplies,
the quality of these waters gradually improved in this most
important respect, as is seen from diagram No. 1. In this
diagram, the continuous line with dots represents the
mortality from typhoid in Manchester, the broken and
eroped line the contemporaneous mortality in London, and
the dotted curve the degree of turbidity of the London
water supply.

1 68 SCIENCE PROGRESS.

These observations graphically represented in the dia-
gram show that, at the time they were commenced, the
filtering operations were carried on with considerable care-
lessness, and that this continued, though to a less extent,
down to the year 1883, since which time, and especially
since 1884, the efficiency of filtration of all the river waters
supplied to the Metropolis has left little to be desired.

What is it then that separates the past from the present
water supply of London ? In the first place there is the
change of source — I mean the change in position of the
intakes of the several Companies drawing from the Thames
and Lea — and the total abandonment of the much-polluted
river Ravensbourne by the Kent Water Company. So
long as the water supply was derived from the tidal reaches
of the Thames and Lea, receiving as these reaches did the
drainage of immense populations, the risk of infection from
water-borne pathogenic organisms could scarcely be other-
wise than imminent ; for, although we now know efficient
filtration to be a perfect safeguard, anything short of effi-
ciency must be attended with risk in the presence of such
extreme pollution.

Nevertheless, the line of demarcation between the past
and the present water supply of the Metropolis is, in my
opinion, to be drawn, not when the intakes of the river
companies were removed to positions beyond the possibility
of pollution by the drainage of London, but it must be drawn
at the time when efficient filtration was finally secured and
ever since maintained, that is to say, in the year 1884.

The removal of turbidity by sand filtration, however,
refers only to suspended matters ; but there are sometimes
objectionable substances in solution of which organic matter
is the most important. River water and mountain water,
even when efficiently filtrated, contains more organic matter
than spring or deep well water; but this is reduced in quantity
by storage and especially by filtration, although these waters
can perhaps never be brought up to the standard of organic
purity of spring and deep well water.

THE WATER SUPPLY OF LONDON.

169

THE PRESENT WATER SUPPLY.

At present London is supplied with water from four
sources — the Thames, the Lea, the New River, and deep
wells. Of these the deep wells yield as a rule the purest
water, requiring no filtration or treatment of any kind before
delivery for domestic use. The river waters, on the other
hand, require some kind of treatment before delivery —
storage, subsidence in reservoirs, and filtration. The water
from the Thames is abstracted at and beyond Hampton, far
above the reach of the tide and London drainage. The
water from the Lea is taken out at two points, viz., at Angel
Road near Chingford, by the East London Water Company,

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and above Hertford by the New River Company, who
convey it to Green Lanes by an open conduit twenty-five
miles long, called the New River Cut, in which it is mixed
with a considerable volume of spring and deep well water.

All three river waters are affected by floods and are, as
raw materials, of considerably different quality as regards
organic purity (see diagram No. 2). From these raw
materials by far the largest volume of the Metropolitan
Water Supply is derived, and the chemical or organic
purity of the water sent out to consumers stands in direct
relation to the organic purity of the raw material used, as

170

SCIENCE PROGRESS.

is seen from the diagrams Nos. 3, 4 and 5, which show the
proportional amounts of organic elements in the raw and
filtered waters ; they also show the advantage of storage
in excluding flood water, No. 4 shows that floods in March

PROPORTIONAL AMOUNT OF CRCANIC ELEMENTS
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arid August were circumvented, but not in November. The
numbers in the margins of the diagrams express the pro-
portional amount of organic elements, that in the Kent

PROPORTIONAL AMOUNT OF ORGANIC ELEMENTS
IN RAW LEA AND EAST LONDON COMPANY'S WATER

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Company's water during the nine years ending December

1876 being taken as unity, as is depicted in diagram No. 5.

Hitherto I have spoken of chemical purity or comparative

freedom from organic matter only, but the spread of diseases

THE WATER SUPPLY OF LONDON.

171

such as cholera and typhoid fever through the agency of
drinking water has no connection whatever with the chemical
or organic purity of the water. These diseases are propa-
gated by living organisms of extreme minuteness, to which
the names bacilli, bacteria, and microbes have been given,
and here comes the important question how, if at all, does
filtration secure immunity from these water-borne diseases ?
To Dr. Koch of Berlin, we are indebted for the answer
to this question. By his discovery of a means of isolating
and counting the number of bacteria, or bacilli, or microbes
and their spores in a given volume of water, we were, for
the first time, put into possession of a method by which the
condition of water as regards these living organisms, before

PROPORTIONAL AMOUNT OF ORGANIC ELEMENTS
IN NEW RIVER AND DEEP-WELL WATERS.

1835

so

No. 5.

and after filtration, can be determined with quantitative
exactness. The enormous importance of this invention
(which was first made known and practised in England in
1882 by the late Dr. Angus Smith) is evident, when it is
borne in mind that the living organisms, harmful or harm-
less, contained in water are of such extreme minuteness as
practically to defy detection by ordinary microscopical
examination. But although the microscope cannot detect
with certainty single bacteria or their spores, even the
naked eye can easily discern towns or colonies consisting of
thousands or even millions of such inhabitants.

Dr. Koch's method accomplishes at once two things :
it isolates, in the first place, each individual microbe or

172 SCIENCE PROGRESS.

germ ; and, secondly, places it in conditions favourable for
its multiplication which takes place with such amazing
rapidity that, even in a few hours, or at most in two or
three days, each organism will have created around itself
a visible colony of innumerable members — a town in fact
comparable to London itself for population.

By operating upon a known volume of water, such as
a cubic centimetre for instance, the number of separate
organisms or their spores, in a given volume of the water
under investigation can thus be determined. The following
is the method now adopted in carrying out Koch's process
for the bacterial investigation of drinking water : —

i. Preparation of the nutritive medium.

2. Sterilisation of the medium.

3. Collection of the sample of water in a vacuous tube

afterwards to be hermetically sealed.

4. Transport of the sample to the bacteriological

laboratory, packed in ice to prevent multiplica-
tion.

5. Mixture of a known volume of the water sample

with the nutrient medium.

6. Casting of the mixture into a solid plate.

7. Incubation of the solid plate.

8. Counting of the colonies.

9. Examination of separate colonies, or rather of the

individual members under the microscope.

Sometimes the cultivations are made upon a plate of
the substance called agar which resembles isinglass, and
bears a temperature of blood heat without melting.

In order to ascertain the effect of filtration upon the
bacterial quality of water, it is absolutely necessary that
the sample should be taken immediately after it has passed
through the filters ; for, if it be obtained from the delivery
mains in town, that is to say, after the water has passed
through many miles of pipes, the rapid multiplication of
these organisms, except in very cold weather is such, that
a water which contains only a single living organism per
cubic centimetre, as it issues from the filter, may contain

THE WATER SUPPLY OF LONDON.

173

100 or 1000 in the same volume when, after several hours,
it arrives on the consumer's premises.

Now what is the effect of sand filtration as carried out
by the various Water Companies supplying London upon
the living matter contained in the raw river water ? // is
simply astounding : water containing thousands of bacteria
per cubic centimetre, for a single drop of Thames water
sometimes contains nearly 3000 separate living organisms,
comes out from the sand filters with fifty, thirty, ten, or even
less of these organisms per cubic centimetre, or the number
of microbes in a single drop is reduced to two or even to zero.

MICROBES IN RAW AND FILTERED THAMES
WATER 1894.

JANUARY

FEBRUARY MARCH APRIL

MAY JUNE

JULY AUCUST SEPTEMBER

OCTOBER

NOVEMBER DECEMBER

No. 6.

MEAN

Rather less than one-tenth of the total volume of water
supplied to London is derived by the Kent Water Company
from deep wells in the chalk. As it issues from the porous
rock into the fissures and headings of these wells, this water
is, in all probability, absolutely sterile ; but by the time it
has been pumped up to the surface it usually contains a
certain number, though small, of microbes. Thus, during
the year 1892 it contained on the average six per cubic
centimetre in 1893, thirteen; in 1894, fifteen; and in
1895, eight.

The diagram No. 6 shows graphically the bacterial
improvement of the Thames water by filtration during

i74 SCIENCE PROGRESS.

the year 1894. ^n this diagram the black squares represent
the number of microbes in a given volume of the raw water
in each month, and the white centres the number remaining
in the same volume after filtration.

Although deep well water has, from a bacterial point
of view, a decided advantage, the filtered river waters
are not very far behind, and there is every reason to believe
that with the improvements which are now being carried out
by the various river Water Companies, the Kent Company's
deep well water will, before long, be run very hard by the
other supplies.

By the examination of the water as it issues from the
filters, the utmost freedom from microbes, or maximum
degree of sterility of each sample is determined. This
utmost freedom from bacterial life after all sources of con-
tamination have been passed is obviously the most
important moment in the history of the water ; for the
smaller the number of microbes found in a given volume at
that moment the less is the probability of pathogenic or
harmful organisms being present ; and although the non-
pathogenic may afterwards multiply indefinitely this is of
no consequence in the primary absence of the pathogenic ;
but it is only fair, in describing the character of the present
water supply of London, to say that not a single pathogenic
organism has ever been discovered even in the ^filtered
water as it enters the intakes of the various Companies,
although these organisms have been carefully sought for.
It is sometimes said that the non-pathogenic organisms
found in water may be beneficial to man ; but this idea is
not borne out by the fact of their entire absence from the
food which nature provides for young animals. Healthy
milk is absolutely sterile.

As it is at present impracticable to obtain water, uni-
formly at least, free from microbes, it is desirable to adopt
some standard of bacterial purity ; and 100 microbes per
cubic centimetre has been fixed upon by Dr. Koch and
myself as the maximum number allowable in potable water.
This standard is very rarely infringed by the London
Water Companies, whilst I have every reason to hope that,

THE WATER SUPPLY OF LONDON. 175

in the near future, now that special attention is directed to
bacterial filtration, it will not be approached within 50 per
cent. This hope is based not only upon my own observations,
but also upon the exhaustive and exceedingly important
investigations carried out at the Lawrence Experiment
Station by the State Board of Health of Massachussetts,
under the direction of Mr. George W. Fuller, the official
biologist to the Board.

More than six years have already been spent in the prose-
cution of these American experiments, and many thousands
of samples of water have been submitted to bacterial cultiva-
tion. The Massachussetts experimental filters are worked at
rates up to 3,000,000 gallons per acre daily, which renders
the results available for application to public water supplies ;
indeed none of the water delivered in London is filtered at
so rapid a rate as this. It was found that at these rates all
the disease-producing germs, which were intentionally and
in large numbers added to the unfiltered water, were
substantially removed. The filters were so constructed
and arranged as to allow direct comparison of the bacterial
purification of water under different rates of filtration, with
sand of different degrees of fineness, with different depths
of the same sand, and with intermittent and continuous
filtration.

The actual efficiency of these filters was also tested by
the application of the bacillus of typhoid fever. Very large
numbers of these bacilli and of other species were applied
in single doses to the several filters at different times, and
the effluent was examined four times daily for several days
afterwards. The results so obtained give a thoroughly
trustworthy test of the degree of bacterial purification
effected by each of the experimental filters, and these are
the data which have been largely used by the Mas-
sachussetts State Board of Health in deducing the rules
which they consider ought to be observed in water filtration.

Among the subjects investigated by means of these
experimental filters were : —

1. The effect, upon bacterial purification, of the rate of
filtration.

176 SCIENCE PROGRESS.

2. The effect of size of sand grains upon bacterial

purification.

3. The effect of depth of material upon bacterial

purification.

4. The effect of scraping the filters upon bacterial

purification.
Time does not permit of my giving the answers to these
questions in detail ; but they may be summarised as follows : —

1. The rate of filtration between 500,000 and 3,000,000
gallons per acre per day exercises practically no effect on
the bacterial purity of the filtered water. It is worthy of
note that the rates of filtration practised by the several
Water Companies drawing their supplies from the Thames
and Lea are as follows: Chelsea Company, 1,830,000;
West Middlesex, 1,359,072 ; Southwark Company, 1,568, 160;
Grand Junction Company, 1,986,336; Lambeth Company,
1,477,688; New River Company, 1,881,792; and East
London Company, 1,393,920. Hence not one of the
London Companies filters at the rate of 2,000,000 gallons
per acre per day ; at which rate in the Massachussett's
filters 99*9 per cent, of the microbes present in the raw
water were removed.

2. The effect of size of sand grains was found to be very
considerable ; and, in confirmation, I find that by the use of
a finer sand than that employed by the Chelsea Company,
the West Middlesex Company is able, with much less stor-
age, to attain an equal degree of bacterial efficiency.

3. The depth of sand, between the limits of one and five
feet, exercises no practical effect on bacterial purity when
the rate of filtration is kept within the limits just specified.
And this result is quite borne out by my own experience
gained in the bacterioscopic examination of the filtered
waters of the seven Companies supplying the Metropolis
from rivers. Thus the New River Company, with i*8 feet
of sand on the filters, compares favourably with the Chelsea
Company, the sand on whose filters is more than twice that
depth.

Placed in the order of thickness of sand on their filters,
the Metropolitan Companies range as follows : Chelsea,

THE WATER SUPPLY OF LONDON. 177

Lambeth, West Middlesex, Southwark, East London,
Grand Junction, and New River. Placed in the order of
efficient filtration they range as follows : Chelsea and West
Middlesex equal, New River, Lambeth, East London,
Southwark, and Grand Junction.

4. When there is such an accumulation of deposit on
the surface of a sand filter that, for practical purposes,
sufficient water cannot be made to pass through it, the
surface of the filter has to be scraped ; that is to say, the
mud and about half an inch of the sand are removed from
the surface. After this operation, there is sometimes an
increase in the number of bacteria in the filtered water, and
it was noticed that the increase was greater in shallow than
in deep filters and with high than with low rates of filtration;
and there is no doubt that the effect of scraping is con-
siderably magnified when coarser descriptions of sand are
employed, as in the case of the filters of the London Water
Companies. I should like, therefore, to impress upon the
engineers of these Companies the desirability of using finer
sands than are at present employed.

INFLUENCE OF THE BACTERIAL CONDITION OF THE RAW
RIVER WATER UPON THAT OF THE FILTERED EF-
FLUENT.

I have found that the number of bacteria in a given
volume of filtered water is to a considerable extent in-
fluenced by the number contained in the raw water supplying
the filter ; and from this point of view, therefore, the bacterial
condition of the raw river water used in the Metropolis is of
no inconsiderable importance.

Since May, 1892, I have made monthly determina-
tions of the number of microbes capable of developing
on a gelatine plate in a given volume of raw Thames water
collected at the intakes of the Metropolitan Water Companies
at Hampton ; and the number has varied during this time
between 631 and 56,630 per cubic centimetre, the highest
numbers having, as a rule, been found in winter or when

178

SCIENCE PROGRESS.

the temperature of the water was low, and the lowest
in summer or when the temperature was high.

Now, besides temperature, there are two other conditions
to either of which this difference may be attributed, viz.y
sunshine and rainfall, and I have endeavoured by a series
of graphic representations to disentangle these possible
influences from each other by placing the results of the
microbe determinations in juxtaposition with (i) the tem-
perature of the water at the time the samples were taken ;

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(2) the number of hours of sunshine on the day and up to
the hour when each sample was drawn and on the two
preceding days, and (3) the flow of the Thames over
Teddington Weir on the same day expressed in millions
of gallons per twenty-four hours. Although the graphic
representations were confined to the Thames, the conditions
affecting bacterial life in this river are doubtless equally
potent in other rivers and streams.

The samples for microbe cultivation were collected at

THE WATER SUPPLY OF LONDON.

179

about nine inches below the surface of the water in partially
exhausted and sealed tubes, the ends of which, when the
tubes were lowered to the required depth, were broken off
by an ingenious contrivance devised by my Assistant, Mr.
Burgess. On being withdrawn from the river the tubes
were immediately hermetically sealed and packed in ice for
conveyance to my laboratory, where the cultivation was
always commenced within four hours of the time of collection.

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No. 8.

For the records of sunshine, I am indebted to the
kindness of Mr. James B. Jordan of Staines ; and for
gaugings of the Thames at Teddington Weir to Mr. C. J.
More, the engineer to the Thames Conservancy Board.

The graphic representation of these collateral observa-
tions affords definite evidence as to which of the three
conditions — temperature, sunshine, and Mow of the river —
has the predominant influence upon bacterial life in the
water. The first diagram (No. 7) compares the number of

13

i8o

SCIENCE PROGRESS.

microbes per cubic centimetre with the temperature at the
time the sample was taken. The horizontal lines express
the numbers of microbes and the temperature, while the
vertical lines denote the months when the samples were
taken. For obvious reasons the horizontal lines express-
ing the numbers of microbes and temperatures are num-
bered in opposite directions.

The diagram shows that although coincidences between
a high number of microbes and a low temperature are not

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wanting, some other condition entirely masks the effect, if
any, of temperature.

The next diagram (No. 8) institutes the comparison
between the number of microbes and the hours of sun-
shine to which the water has been exposed. The diagram
is constructed on the same lines as the first.

It is here seen that, as in the case of temperature,
there is some other condition which entirely overbears the
influence of sunlight in the destruction of microbes in the

THE WATER SUPPLY OF LONDON. 181

river water. This condition is the amount of rainfall higher
up the river, or, in other words, the volume of water flowing
along the river bed, as is seen from the comparison repre-
sented in the next diagram (No. 9).

This diagram shows very conclusively that the volume
of water flowing in the Thames is the paramount influence
determining the number of microbes. It compares the
volume of water in the river gauged at Teddington Weir
with the number of microbes found in the raw Thames
water at Hampton on the same day. In this diagram, the
numbers representing the flow of the river in millions of
gallons per day and the number of microbes per cubic
centimetre in the water both run from the bottom of the
diagram upwards.

Comparing the curves in the diagram it is seen that,
with very few exceptions, a remarkably close relation is
maintained between them.

The only exception of any importance to the rule that
the number of microbes varies directly with the flow of
the river, occurring during the thirty-two months through
which these observations were continued, happened in
November, 1892, when the flow increased from 501 mil-
lions of gallons in October to 1845 millions in November,
whilst the microbes actually diminished in number from
2216 to 1868 per cubic centimetre. Neither the sunshine
nor the temperature records of these two months, however,
afford any explanation of this anomalous result, for there
was a good deal of sunshine in October before the collection
of the sample and the temperature was higher, whilst in
November no ray of sunshine reached the Thames during
the three days preceding the taking of the sample and the
temperature was nearly 40 C. lower than in the preceding
month. I have ascertained, however, that the Thames
basin had been twice very thoroughly washed out by heavy
floods before the time when the November sample was
taken, and this affords a satisfactory explanation of the
anomalous result yielded by this sample.

These comparisons demonstrate that the number of
microbes in Thames water depends directly upon the rate

182

SCIENCE PROGRESS.

of flow of the river, or, in other words, on the rainfall, and
but slightly, if at all, upon either the presence or absence of
sunshine or a high or low temperature ; and they are con-
firmed by the continuation of these observations during the
year 1895 exhibits in diagram No. 10.

With regard to the effect of sunshine upon bacterial
life, the interesting observations of Dr. Marshall Ward
leave no doubt that sunlight is a powerful germicide ; still
it is obvious that its potency in this respect must be greatly
diminished, if not entirely annulled, when the solar rays
have passed through a stratum of water of even com-

MICROBES and FLOW of THAMES

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No. 10.

paratively small thickness before they reach the living
organisms. By a series of ingeniously contrived experi-
ments, Mr. Burgess has demonstrated the correctness of
this view.

A sterile bottle about half filled with Thames water was
violently agitated for five minutes to insure equal distribu-
tion of the organisms. Immediately afterwards a number
of sterile glass tubes were partially filled with this water
and sealed hermetically. Three of these tubes were
immediately packed in ice, and the remainder were attached
in duplicate at definite distances apart to a light wire frame
which was then suspended vertically in the river. The

THE WATER SUPPLY OF LONDON. 183

experiments were made near the Grand Junction Company's
Intake at a place favourable for the sun's rays to fall on the
river without any obstruction.

The river was at the time in a very clear condition and
contained but little suspended matter ; whilst the day was
fine, although clouds obscured the sun occasionally. The
tubes were exposed to light in the river for four and a half
hours — from ICV30 a.m. to 3 r.M. on 15th May, 1895. At
the end of this time the tubes were packed in ice for trans-
port to my laboratory, where the cultivation was started
immediately. The colonies were counted on the fourth day
and yielded the results given in the table : —

No. of Colonies
per c.c.
Thames water packed in ice immediately after collection - 2127
Thames water after exposure to sunlight for 4^ hours at

surface of river ------- 1140

Thames water after exposure to sunlight for 4^ hours at

6 in. below surface of river ----- i^o

Thames water after exposure to sunlight for 4^ hours at

1 ft. below surface of river - - - - - 2150
Thames water after exposure to sunlight for 4J hours at

2 ft. below surface of river ----- 2430
Thames water after exposure to sunlight for 4! hours at

3 ft. below surface of river ----- 2440

These experiments show that, on 15th May the
germicidal effect of sunlight on Thames microbes was nil
at depths of one foot and upwards from the surface of the
water. It cannot, therefore, excite surprise, that the effect
of sunshine upon bacterial life in the great mass of Thames
water should be nearly, if not quite, imperceptible. It is
thus ascertained that sunlight can only kill the germs, or
microbes, near the surface of the water, whilst those at any
depth, for the most part, escape destruction.

On the other hand the enormous effect of floods in
augmenting the number of microbes can hardly surprise us,
for when a great body of water has flowed over the banks
of the river, which are at other times dry and exposed, it
carries along with it countless impurities — an effect common
both to the main stream and its tributaries. The Thames

184 SCIENCE PROGRESS.

basin is as it were, on every such occasion, thoroughly-
washed out, and it is only to be expected that the number
of microbes in the water should be enormously increased as
is found to be the case.
Now with respect to

THE WATER SUPPLY OF THE FUTURE.

In view of the rapid increase of the population of Lon-
don, fears have from time to time been entertained that the
water supply from the Thames basin, that is to say from
the rivers Thames and Lea, supplemented by water from
springs and deep wells within the basin itself, would soon
be insufficient in quantity ; whilst the quality of the
water taken from the river has, up to a comparatively
recent date, been considered unsatisfactory. On these
grounds various schemes have, from time to time, been
brought forward for the supply of the Metropolis from
other river basins — from the Wye, the Severn, the river
basins of North Wales, and of the Lake Districts of
Cumberland and Westmoreland.

It is worthy of note, however, that all the Royal Com-
missions have arrived tinanimously at the conclusion
that the quantity of water obtainable from the Thames
basin is so ample as to render the necessity of going else-
where a very remote contingency.

I shall now endeavour to put, very shortly before you
a few facts which, in my opinion, prove that, both as
regards quantity and quality, the Thames basin will for a very
long time to come afford an abundant supply for the Metro-
polis. There is indeed no river basin in Great Britain
which affords such an abundant supply of excellent water
as that available in the Thames basin.

Besides that which flows directly into the rivers, this
water is contained in the Chalk, Oolite, and Lower Green-
sand, which are the best water bearing strata in the
kingdom. From these rocks it issues in copious springs
of unsurpassed organic purity. I have personally inspected
every spring of importance in the Thames basin and have

THE WATER SUPPLY OF LONDON.

185

analysed samples of the water. The results, in a very con-
densed form, are recorded in the annexed Table. Twenty-

SPRING AND DEEP-WELL WATERS IN THE THAMES

BASIN.

Results of Analysis in
Parts per 100,000.

Oolite.

Average of 21

Samples.

Lower

Greensand.

Average of 5

Samples.

Chalk.

Springs.

Average of 8

Samples.

Wells.

Average of 36

Samples.

Total Saline Matters -
Organic Carbon - -
Organic Nitrogen - -
Hardness before boiling

after

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one samples of Oolitic spring- water were analysed, and
every one of these was of even greater organic purity
than the water delivered by the Kent Company, which I
have always regarded as the standard of organic purity to be
aimed at in all other Water Works.

Five springs issuing from the Lower Greensand were
examined ; and again, every one of these was of even
greater purity, organically, than the Kent Company's
water ; whilst they were, on the average, only one-third as
hard. Forty-six samples of water from the Chalk were
chemically examined, and these also contained but the
merest traces of organic matter.

All these samples from the Chalk were derived from
sources where the water-bearing- stratum is free from a
covering of London clay ; but, as soon as the Chalk dips
beneath the London Tertiary Sands and clay, the quality of
the water undergoes a remarkable alteration. The total
solids in solution are greatly increased in amount, whilst
the hardness is much mitigated, owing to the replacement
of bicarbonate of lime by bicarbonate of soda. These
waters are also of high organic purity ; but, as the quantity
is very limited, it is useless to dwell upon them. They

186 SCIENCE PROGRESS.

supply the Trafalgar Square fountains and the London
breweries, and we can well afford to leave them to be con-
verted into beer. For dietetic purposes there is no better
water in the kingdom than the underground water of the
Thames basin. For sentimental reasons I should like to
see it conveyed to the works of the various companies in
special conduits ; but we have seen that, on hygienic
grounds, it may safely be allowed to flow down the bed of
the Thames if it be afterwards efficiently filtered.

So much for quality, now as to quantity ; the basins of
the Thames and Lea include an area of upwards of 5000
square miles. Of this rather more than one half (including
the Oolitic, Cretaceous, and portions of the Tertiary Forma-
tions) is covered by a porous soil upon a permeable water
bearing stratum. The remainder is occupied by the
Oxford, Kimmeridge, Gault, and London Clays ; being
thus covered by a clay soil upon a stiff and impervious
subsoil.

The annual rainfall of the district is estimated at an
average of twenty-eight inches. The rivulets and streams
of the Thames basin are formed and pursue their course on
clay land. There are no streams on the Chalk. That
which falls upon this porous stratum and does not evaporate
sinks, mostly where it alights, and heaps itself up in the
water-bearing stratum below, until the latter can hold no
more. The water then escapes as springs at the lowest
available points.

Innumerable examples of these springs occur all round
the edge of the Thames basin, and at various points within
it. Thus from the Chalk they are ejected at the lip of the
Gault ; and in the Oolitic area by the Fuller's Earth below
it, or by the Oxford Clay, geologically, above it.

According to the guagings of the engineer of the
Thames Conservancy Board there passed over Teddington
Weir, in 1892, 387,000 millions of gallons, equal to an
average flow of 1060 millions of gallons daily. In the
following year, 1893, their passed over Teddington Weir
an aggregate of 324,227 millions of gallons, or a daily
average of 888 millions, the average for the two years being

THE WATER SUPPLY OF LONDON. 187

974 millions of gallons, and this number does not in-
clude the 1 20 millions daily abstracted by the five London
Water Companies who draw their supplies from the
Thames.

Thus, in round numbers, we may say that after the
present wants of London have been supplied from this
river, there is a daily average of nearly 1000 millions of
gallons to spare. Surely it is not too violent an assumption
to make that the enterprising engineers of this country can
find the means of abstracting and storing for the necessary
time one-fourth of this volume.

As regards the quality of this stored water, all my
examinations, of the effect of storage upon the chemical and
especially upon the bacterial quality, point to the conclusion
that it would be excellent. Indeed the bacterial improve-
ment of river water by storage for even a few days is
beyond all expectation. Thus the storage of Thames water
by the Chelsea Company for only thirteen days reduces
the number of microbes to one-fifth the original amount,
and the storage of the river Lea water for fifteen days,
by the East London Company, reduces the number on the
average from 9240 to i860 per cubic centimetre or to one-
fifth ; and lastly, the water of the New River Cut, con-
taining on the average 4270 microbes per cubic centimetre
contains, after storage for less than five days, only 18 10,
the reduction here being not so great, partly on account
of the shorter storage, but chiefly because the New River
Cut above the point at which the samples were taken, is
itself a storage reservoir containing many days' supply after
filtration. Indeed quietness in a subsidence reservoir is,
very curiously, far more fatal to bacterial life than the most
violent agitation in contact with atmospheric air ; for the
microbes which are sent into the river above the falls of
Niagara, by the City of Buffalo, seem to take little or no
harm from that tremendous leap and turmoil of waters,
whilst they subsequently, very soon, almost entirely dis-
appear in Lake Ontario.

It is not, therefore, too much to expect that storage for,
say a couple of months, would reduce the number of

188 SCIENCE PROGRESS.

microbes in the Thames flood water down to nearly the
minimum ever found in that river in dry weather, whilst,
by avoiding the first rush of each flood, a good chemical
quality could also be secured.

There is, therefore, I think, a fair prospect that the
quantity of water derivable from the Thames at Hampton
could be increased from its present amount (120 millions of
gallons per diem) to 370 millions.

Again, in the river Lea, although here the necessary
data for exact calculations are wanting, it may be assumed
that the present supply of 54 millions of gallons could
be increased by the storage of flood water to 100
millions per day. To these volumes must be added the
amount of deep-well water which is attainable from those
parts of the Thames basin which lie below Teddington Lock,
and in the Lea basin beloiv Lea Bridge, and which was
estimated by the last Royal Commission at rather more
than 67J millions of gallons.

Thus we get the grand total of 53735- millions of
gallons of excellent water obtainable within the Thames
basin, the quality of which can be gradually improved, if it
be considered necessary, by pumping from the water bear-
ing strata above Teddington and Lea Bridge respectively,
instead of taking the total supply from the open rivers
above these points. Such a volume of water would scarcely
be required for the supply of the whole water area of Lon-
don at the end of fifty years from the present time, even
supposing the population to go on increasing at the same
rate as it did in the decade 1881-91, which is an assumption
scarcely likely to be verified.

In conclusion, I have shown that the Thames basin can
furnish an ample supply for fifty or more years to come,
whilst the quality of the spring and deep-well waters and of
the filtered river water would be unimpeachable. To secure
these benefits for the future, storage must be gradually pro-
vided for 1 1,500 millions of gallons of flood water judiciously
selected in the Thames Valley, and a proportionate volume
in the basin of the Lea ; whilst filtration must be carried to
its utmost perfection by the use of finer sand than is at

THE WATER SUPPLY OF LONDON. 189

present employed, and by the maintenance of a uniform rate
during the twenty-four hours.

There is nothing heroic in laying pipes along the banks
of the Thames, or even making reservoirs in the Thames
basin. They do not appeal to the imagination like that
colossal work, the bringing of water to Birmingham from
the mountains of Wales, and there is little in such a scheme
to recommend it to the minds of the enterprising engineers
of to-day. Nevertheless, by means of storage, by utilising
springs, by sinking deep wells, and by such comparatively
simple means, we have, in my opinion, every reason to con-
gratulate ourselves that for half a century at least we have
at our dooi's, so to speak, an ample supply of water which for
palatability, wholesomeness, and general excellence will not
be surpassed by any supply in the world.

E. Frankland.

SOME RECENT MEMOIRS UPON
OLIGOCH^TA.

THE literature relating to this group of worms is
summed up in my Monograph of the Oligochceta
lately issued by the Clarendon Press ; but so energetic are
the unfortunately somewhat few workers in this particular
subject that new facts have gone on accumulating with some
rapidity since the publication of that work. It is my
intention in the present article to offer the reader a re'sume
of this latest work with, naturally, some references to what
has gone before.

It is agreed by all those who are acquainted with the
terrestrial Oligochaeta that their peculiar mode of life, their
susceptibility to sea water, and the comparatively few
chances of dispersal enjoyed by them, render their distribu-
tion highly important in estimating the relations between
land masses now and in the past. This has an especial
bearing upon the theory of the former northward extension
of the Antarctic Continent, a matter upon which much has
been written lately. To deal adequately with this large
question would of course demand more space than can be
allowed me. I shall content myself with referring solely to
the evidence which is forthcoming from the study of earth-
worms. Fortunately we are in possession of a considerable
amount of information about the terrestrial Olioochaeta of
New Zealand and Patagonia ; the former country indeed
must be regarded as being better known perhaps than any
quarter of the globe, excepting of course Europe. The
extensive collections lately made by Dr. Michaelsen in
South America have added largely to the number of species
brought back by his predecessors. It results from an
examination of the species found in the two countries that
in both of them the prevailing types belong to the genera
Acanthodrilus and Microscolex, particularly the former. Of
the thirty-two indigenous species at present known from
Patagonia and the more southern parts of the South Ameri-

SOME RECENT MEMOIRS UPON OLIGOCH/ETA. 191

can Continent, twenty are members of the genus Acantho-
drilus, eleven are Microscolex and one is a PericJiesta. Besides
these are a few obviously imported Lumbricus and
Allolobophora from Europe or North America. I say
obviously imported because these worms are only found in
cultivated ground and near the coast ; as civilisation is left
behind these species decrease and are replaced by the
truly indigenous species. Among the twenty species of
Acanthodrilus are included two or three which occur in the
Falkland Islands and in South Georgia. Turning to New
Zealand we find that out of twenty indigenous species nine
are Acanthodrilus, six belong to the closely allied genera
Octochcehis, Deinodrilus, and Plagiochcsta, three are Micro-
scolex, while the two remaining are a Perichceta and a
Megascolides, two genera which are eminently characteristic
of the adjoining continent of Australia. Between New
Zealand and South America is a long stretch of ocean,
sparsely scattered over which are islands of volcanic origin.
From three of these islands earthworms have been collected.
In Kerguelen and Marion Island is a species of Acantho-
drilus peculiar to those islands, and I have lately received,
and am describing in the forthcoming June number of the
Proceedings of the Zoological Society, a second species of
that genus from Macquarie Island. The significance of
these facts will be more apparent when we consider how
far the genera that have been referred to in the fore-
going are distributed outside of this antarctic area. Micro-
scolex is found in many parts of central and the warmer
western regions of North America ; it has been met with
also in Europe, Algeria and Teneriffe. Acanthodrilus
occurs in Australia where it is represented by three species,
all of which however inhabit the eastern half of the island
continent, that part in fact which is nearest to New
Zealand ; Acanthodrilus has one species in Natal, one in
New Caledonia and two in North America.

We have evidently therefore a fauna of earthworms
peculiar to the antarctic region, into which more northern
forms have been able to make but slight inroads and from
which but few stragglers have wandered.

i92 SCIENCE PROGRESS.

As to other distributional facts and theories, it is
probable that I have underestimated in my Monograph the
distinctness of the Palaearctic and the Nearctic regions of
Mr. Sclater. I was disposed to unite them into one Hol-
arctic as Professor Newton has called it. Further investi-
gations have tended to emphasise the justice of separating
these two regions. This evidence has been mainly collected
by the industry of Dr. Gustav Eisen, of San Francisco ;
but others whose names and memoirs will be found quoted
in the list of literature at the end of this article have added
details of importance. The North American continent is
inhabited by a fair number of peculiar genera, of which
Diplocardia, originally described some years since by
Garman, has four species (partly referred to the undoubtedly
synonymous genus Geodrilus) ; there are also peculiar to
this region Phoenicodrilus, nearly related to the central
and South America Ocuerodrilus, and Sparganophilus ; of
this latter genus the original species was found by
Benham in the Thames ; but as there are half a dozen
American species it seems likely that its occurrence in
England is a case of importation. Bimastos is a genus
perhaps justly separable from Allolobophora, from which it
chiefly differs in the large size (for a Lumbricid) of the
glandular sac in which the efferent male ducts terminate.
Besides these peculiar genera are a few species of the
Central and South American genera Ocuerodrilus and
Kerria, and of the almost world-wide Benhamia. Aleodrilus
is an Acanthodrilid that Eisen is disposed to separate from
Diplocardia ; two species of Acanthodrilus complete the
list of non-European inhabitants of the North American
Continent. But in addition to these are a number of Allolo-
bophora and Lumbricus — the characteristic forms ol the
Palaearctic region — two or three of which are, however, so
far as our present knowledge goes peculiar to North
America. These facts perhaps justify the retention of
the Nearctic region, and they are perhaps also significant
in that the peculiar forms are western in range — a possible
indication of their approaching extirpation by European
species introduced by commerce.

SOME RECENT MEMOIRS UPON OLIGOCHJETA. 193

The original indigenous forms, South American in
character, may be regarded as having been gradually
driven to the west by the encroachment of artificially in-
troduced species. In other respects the geographical regions
indicated by the distribution of earthworms agree fairly well
with the generally received scheme of Mr. Sclater. The
Ethiopian region is peculiarly distinct ; the Neotropical is
also nearly if not quite as plainly marked ; but the Oriental
fades into the Australian, and it is indeed not easy to
separate them at all.

The only other matter affecting the distribution of earth-
worms with which I shall deal here is the question of
oceanic islands. Our information upon the subject is not
however by any means extensive ; the largest collection
made is due to the energy of Mr. Perkins, and has been
described by me in a paper communicated to the Zoological
Society. These worms were gathered in the Sandwich Is-
lands, and belong to a number of species of which only two
(and a doubtful third) have not been found elsewhere ;
these two belong to the genus Perichccta, a genus prevalent
in tropical regions, especially of the old world. That the
bulk of the species known from these and other oceanic
islands are forms which have been in all probability intro-
duced by accidental transference by man is rather what might
be expected from the limited powers of independent travel
possessed by these animals. There is at present no certain
evidence that there are any truly indigenous earthworms in
oceanic islands, with the exception of Kerguelen — a fact
which as I have already hinted may be due to other causes.

To Linnaeus only a single species of earthworm was
known, his Liimbricus terrestris, now believed to have beeii
a compound of more than one species. Grube in his
Familie der Anneliden, published in 1851, reckoned up
only forty-two earthworms, and of these one or two are
now known not to be earthworms at all, and of the re-
mainder many are unrecognisable or synonyms. Since that
period the increase of new forms has gone on — of late
with extreme rapidity ; at the present moment we are
acquainted with rather over 500 distinct and well char-

i94 SCIENCE PROGRESS.

acterised species. And this estimate does not take into
consideration subspecies or well marked varieties, and pays
no attention to " species incertae ". Of aquatic Oligochceta
150 is about the number of known species ; but this
group is decidedly less known than the former. As with
other groups of animals this great increase in the number
of known species has added to our knowledge of anatomical
fact, but rendered harder the formation of classificatory
schemes. No indistinctness, however, has arisen to blur
the perfectly sharp outlines of the group Oligochaeta, no
''intermediate" forms have been discovered whose relega-
tion to the group is a matter of uncertainty or convenience.
At the same time a few approximations in structure to the
leeches on the one hand, and to the Polychseta on the
other have been discovered ; but these are in no case of
first-rate importance. Perhaps the most remarkable is the
description of the gills of the African genus Alma. This
worm was originally described under that name by Grube
in 1855. Thirty-four years later Levinsen, apparently in
ignorance of Grube's paper, named a fragment of what was
obviously the same worm Digitibranckus, and described in
the same paper Siphonogaster, an Annelid characterised by
a pair of long processes an inch or so in length, and of a
spatula-like form arising from the eighteenth segment.
These have been subsequently shown to be processes con-
taining the outer section of the sperm duct which opens
near to the extremity. Michaelsen showed that all these
three worms are identical, and has thus been able to put
beyond question the existence of a true earthworm l with
branched retractile gills on the posterior segments of the
body. It was not by any means clear from the earlier
descriptions that the gilled worm was not a Polychaet.
Among the lower aquatic Oligochsetes there are at least
three gilled forms, apart from Dero which has a circlet
of ciliated processes, with vascular twigs lying round the
anus. These forms are Chcstobranckus of Bourne, and
Branchiura and Hesperodrilus branchiatus of myself. In

1 Structurally ; in habit it is aquatic.

SOME RECENT MEMOIRS UPON OLIGOCHJETA. 195

the two latter (which are allied to Tubifex) are contractile
branchiae, not branched however, on some of the posterior
segments of the body. More numerous are indications of
affinity with the leeches. I may, in the first place, refer
to that group of parasitic Oligochaeta, once placed among
the leeches but now usually allowed to be true Oligochaeta,
for which Vejdovsky has proposed the name of Disco-
drilidae on account of their posterior sucker. An American
genus Bdellodrilus has lately been studied with care by
Moore whose results entirely confirm the placing of the
worms amono- the Oligochaeta and their removal from the
leeches. Their chief points of likeness to the Hirudinea are
(1) absence of setae ; (2) existence of jaws ; (3) presence of a
sucker ; (4) median unpaired character of reproductive pores.
The first and last of these characters are, however,
found in a few undoubted Oligochaeta, for instance, Anachczta,
as its name denotes, has no setae, and besides Mr. Moore
describes large gland cells in Bdellodrilus which may re-
present setigerous cells of Oligochaeta. As to the median
generative pores they are very frequent among Oligochaeta.
The reproductive organs themselves are decidedly upon the
Oligochaetous pattern. The gonads are entirely free from
their ducts, and there is a single spermatheca, a structure
entirely wanting among the true leeches. The male ducts
are two pairs, opening freely by ciliated mouths into the
coelom and uniting into a common terminal atrium. Their
arrangement recalls that of the Lumbriculidae. The ovaries
are proliferations of the coelomic walls and their contents
escape to the exterior by a slit in the body walls lined by
epithelium, a kind of rudimentary oviduct paralleled in the
Enchytraeidae, and in the Eudrilid Nentertodrilus. There
is nothing leech-like about the reproductive organs, except-
ing the terminal penis — a structure, however, which is
also found in many Eudrilids and in some other Oligo-
chaeta. The conclusions of the author that the Disco-
drilidae are Oligochaeta slightly modified for a parasitic
life is quite borne out by their structure. We may admit
at the same time that this modification is in the direction
of the leeches.

14

196 SCIENCE PROGRESS.

In addition to questions of relationship to other neigh-
bouring groups, recent investigation has brought to light
facts of interest in the anatomy of the Oligochaeta which
bear upon the mutual affinities of the families and genera
into which the order is divided. In this direction the main
discoveries of importance relate to the excretory system. In
all the simple aquatic genera each segment of the body
contains a single pair of nephridia ; as a rule these organs
are wanting in the anterior segments, and Professor Bourne
was unable to find any nephridia at all in Uncinais littoralis.
The absence of nephridia in the anterior segments of the
body, however, also characterises certain earthworms. It
was originally described by Perrier in Pontodrilus, and all
the species of this genus (6) are in the same condition.
More recently Benham and Risen have shown that the
same state of affairs characterises the aquatic Geoscolecid
Sparganophilus. A distinction therefore between the
Limicolae and Terricolse of Claparede quite breaks down.
That these genera have no gizzard or calciferous glands
(or at most the rudiments of a gizzard) is evidence of general
degradation, which may have something to do with their
aquatic or semiaquatic existence. It suggests too that
the simplification in structure of the Limicolae of Claparede
may be rather due to degeneration than to the retention of
primitive characters.

Among the earthworms, however, the single pair of
nephridia to each segment is far from being the rule. In
a large number of genera the nephridia are multiple. Two
pairs in each segment exist in BracJiydriliis ; three pairs in
Trinephrus; and Eisen has lately shown that in certain
North American Benhamias there may be three or four
distinct and separate pairs each with its own internal funnel
and external pore. The complexity of the excretory
system culminates in Perichceta where a single segment may
be furnished with probably at least one hundred external
nephridiopores. It is, however, a question whether in
this latter case there is really an intercommunication be-
tween the several nephridia of each segment, and between
those of adjacent segments as has been alleged by Spencer

SOME RECENT MEMOIRS UPON 0L1G0CHJETA. 197

and myself. The matter requires renewed investigation.
In any case Bourne, Vejdovsky and I have shown that the
" plectonephric " condition, as Benham has termed these
diffuse nephridial tubes, is preceded by a series of paired
nephridia one pair to each segment. This has been proved
in Pericktzta, Qciochcetus and Megascolides. The nephridium
elongates and becomes thrown into loops, each loop finally
appears in Megascolides to break away and to form a
distinct and separate nephridium. It is clear, therefore,
that whether or not the connection is retained in Octochcetris
and Perichceta there is originally a connection, so that that
matter is of less importance than the alleged intercom-
munication from segment to segment. This multiple
arrangement of the nephridia is only found in the families
Acanthodrilidae, Perichsetidae and Cryptodrilidae, and is the
principal argument for uniting them into one superfamily,
Megascolicides, as I have done in my Monograph. Brachy-
drihts, however, is a member of the family Geoscolicidse,
but it has only two pairs of nephridia to each segment ;
there is nothing like the complicated system of Perichceta.
This family Geoscolicidse has been through the recent re-
searches of Rosa and Michaelsen brought still nearer to the
Lumbricidse. It was always difficult to separate them,
mainly on account of the aquatic Criodrilus, now it is
practically impossible unless we accept Michaelsen's inter-
mediate family Criodrilidse. The ornament setae which
used to be a distinctive mark of the Geoscolicidse have
been found by Michaelsen in Allolobophora moebii and
in A. lonnbergi ; many Geoscolicidae, e.g., Microckceta are
distinguished by the fact that instead of a single pair
of spermathecae in each of those segments which con-
tain them there are a considerable number of minute
pouches ; this distinction, however, falls to the ground
since more than one Allolobophora is now known to
possess the same character — which has moreover been met
with in Perichceta. It is in these two families that most
instances are met with of total absence of spermathecae ;
Kynotus, a Madagascar genus, is anteclitellian like the
Lumbricidae, and in short it seems impossible to lay down any

ig8 SCIENCE PROGRESS.

set of characters which should absolutely separate the two
families. Several members of the two families are aquatic ;
thus among the Geoscolicicke Bilimba (with which Michaelsen
now suggests to unite Horst's A nnadri/us and Glyphidrilus),
Criodrilus, whose range the same author has lately ex-
tended to South America, Alma and Sparganophilus. Of
Lumbricidae Allurus is the only form which is often
aquatic. Michaelsen has dwelt upon the fact that all of
these, with the exception of Sparganophilus, have the
body generally or at least the posterior region markedly
quadrangular in outlines with the setae implanted at the
four corners. This is an apparent consequence or at least
concomitant of aquatic life which is more curious than
explicable. So much then for recent modifications of the
systematic arrangement of the group. I shall deal finally
with various anatomical and histological discoveries which
have a general interest unconnected with systematic rela-
tions. The most important work under this heading is
undoubtedly the recent investigations into the structure of
the remarkable family Eudrilidae, a well-defined family
whose boundaries have not become in the least indistinct
by the discovery of new forms. The family is remarkable
on account of its distribution as well as on account of
certain anatomical peculiarities. It is limited to tropical
Africa — to the Ethiopian region of Sclater, with the sole
exception of the type genus Eudrilus, whose ubiquitous-
ness, however (America, West Indies, India and the East
generally, New Zealand, etc.), makes one suspect direct
transference by man. This family is chiefly interesting on
the anatomical side by reason of the illustration which it
gives of two phenomena, viz., substitution of organs and
change in function of organs.

In all Oligochaeta the ovaries are paired (rarely
unpaired) structures which arise from the peritoneal
epithelium of the earthworms invariably the thirteenth
segment. They are totally unconnected with the oviducts
whose open mouths are placed exactly opposite to them.
In the Eudrilidae these gonads are enclosed in sacs
which communicate with a system of sacs the complexity of

SOME RECENT MEMOIRS UPON OLIGOCHMTA. 199

which varies in different genera, and of which it would be
impossible to give any detailed account without the assis-
tance of figures. There is a separate receptaculum ovorum
like that of the common earthworm, with which is connected
the oviduct. This system of sacs, through which the ova
can travel in so far as there are no physical hindrances, also
contain sperm, and play the part of spermatheca? or a sperma-
theca. They commonly open by a single ventral pore ;
sometimes the structures are paired as in the genus Eudrilus
itself. Now these pouches generally contain sperm, and
there is therefore the possibility of the ova being impreg-
nated within them ; Michaelsen has even suggested that
some species are viviparous. In a few genera, for example
in Heliodrilus, these pouches do not communicate with the
exterior except through the oviducts. They appear to do
so by a large ventral pore, but when careful sections are
made it is found that this pore is the mouth of a closed sac,
exactly like a spermatheca, which is enclosed within the
large pouch. Thus the ccelomic nature of this system of
sacs is established on anatomical grounds, and develop-
mentally they have been shown, at least in one genus, to
be derivatives of the intersegmental septa just as are the
sperm sacs of other earthworms ; their cavities are therefore
separated portions of the general ccelom. But, as already
mentioned, in most cases they do open on to the exterior
directly by a conspicuous orifice, and contain sperm which
probably finds its way into them by this orifice. The fact
that in some cases these sacs contain structures which are
precisely like the spermathecae of other earthworms, and
that in other cases where they open directly on to the
exterior the character of the lining epithelium changes near
to the orifice, becoming distinctly columnar, suggests that
we have to do here with the substitution of sacs derived
Irom the septa for the true spermathecae which are gradually
disappearing, only the extremity being left in the majority
ot cases. The second point with which I wish to deal
concerns the calciferous glands. Most, but by no means
all, earthworms possess one or more pairs of these organs,
which are attached to and open into the cesophagus. What-

200 SCIENCE PROGRESS.

ever may be their functions they contain crystals of car-
bonate of lime, and have a rich vascular supply, the lining
epithelium being much folded and therefore extensive. In
some Eudrilidae these structures are absent or rather are so
altered that they are nearly unrecognisable as calciferous
glands. At the same time they have become more numerous.
The structure is altered in that instead of an extensive lumen
produced by the folding of an excretory epithelium there is
a very short sac connected with the oesophagus, which
is, however, enveloped by an extensive coating of cells
which I regard as ccelomic cells, and among which meander
abundant blood-vessels. These ccelomic cells, where they
abut upon blood-vessels, very often lose their oval or
rounded form and become columnar and at the same time
more darkly staining. They surround the blood-vessel as if
it were the lumen of a secreting gland, the cells themselves
having acquired the appearance of a secreting epithelium.
These phenomena suggest that we have to do here with a
change of function on the part of the calciferous glands ; that
their function of producing carbonate of lime, that their
connection with alimentation has disappeared or is dis-
appearing, and that a new function more intimately connected
with the vascular system has supervened. There is a
certain analogy here with the vertebrate liver which has
certainly more functions than that of pouring bile into the
intestine, though originally it may have been merely an
annex of the alimentary canal.

In histology there is only one matter to which I shall
direct the attention of the reader. It concerns the minute
structure of muscular fibres in the Oligochoeta. The careful
researches of Cerfontaine have established the fact that the
Oligochseta, like the leeches, have muscular fibres which
consist of an outer sheath often radiately striated, the
muscular substance, and a soft central core. Hesse, how-
ever, while admitting this, goes a step further and
endeavours to prove a resemblance to the muscular fibres
of the Nematoidea. He figures in the Enchytraeidae and
in the Lumbricidse a gap in the sheath of the fibre through
which the soft less-modified protoplasm of the interior com-

SOME RECENT MEMOIRS UPON OLIGOCH^ETA. 201

municates with a pear-shaped nucleated body outside. If
these observations prove ultimately to be correct it is clear
that there is a close resemblance in this particular between
the Oligochseta and the Nematoidea.

BIBLIOGRAPHY.

Beddard. A Monograph of the Order Oligochseta, Oxford :

Clarendon Press.
ElSEN. Pacific Coast Oligochaeta. Mem. Calif. Acad. Set., vol. ii.,

1895-96.
Hesse. Beitrage zur Kenntniss des Baues der Enchytraeiden.

Zcitschr. fur iviss Zoo/., 1893.
HESSE. Zur vergleichenden Anatomie der Oligochaeten. Ibid.,

1894.
MlCHAELSEN. Zur Kenntniss der Oligochaeten. Abh. Nat. Ver.,

Hamburg, 1895.
H. F. MOORE. On the Structure of Bimastos palustris. Journ.

Morph., 1895.
J. P. MOORE. The Anatomy of Bdellodrilus illuminatus. Ibid.
ROSA. Allolobophora dugesii. Boll. Mus. Zooi, Torino, 1895.
BOURNE. In Quart. Journ. Micr. Sci., 1894.
SMITH. Notes on Species of North American Oligochaeta. Bull.

Illinois State Lab.

F. E. Beddard.

NOTES ON ATOMIC WEIGHTS.

IN a former article 1 a sketch of the state of our know-
ledge as to the relative atomic weights of hydrogen and
oxygen was given. It was there shown that although the
great mass of the evidence was in favour of the atomic
weight of oxygen being about 15*88 times that of hydrogen
yet there was a certain amount of experimental work by
well-known and tried observers which seemed irreconcilable
with this result, the chief paper (1) being that of Professor
Julius Thomsen of Copenhagen, and based on the propor-
tion by weight in which ammonia and hydrochloric acid
combine to form neutral ammonium chloride. In a short
paper by the late Lothar Meyer (2) it was proved con-
clusively how little value could be attached to a determina-
tion of this nature however accurate and careful the mani-
pulative work might be.

Any hopes which might have survived in the minds of
the most ardent follower of Prout, that the atomic weight
of oxygen is exactly sixteen times that of hydrogen, must
now be dispelled by the recent publications of E. W.
Morley (3) and of Thomsen (4) himself. The work of
Morley is so conclusive, and has been carried out with
such untiring patience and skill, that to any one who reads
the clear account which he gives of his methods and of the
various checks employed, it must be quite evident that that
type of worker of whom we regard Stas as the chief is not
yet extinct, in spite of the prevailing view that one must
publish as many papers as possible in the least possible
time before one can be said to engage in " original re-
search ". Morley's scheme for the complete determination
of the relative atomic weights of oxygen and hydrogen is
a most ambitious one, and, although his results are quite
conclusive now, it is much to be regretted that bad health
and other circumstances over which he had no control
(such as a workman pushing a brick through a wall on to a

1 August, 1894.

NOTES ON ATOMIC WEIGHTS. 203

delicate piece of glass apparatus) have up to the present
time prevented him from carrying out his original pro-
gramme in its entirety.

The paper consists of four distinct parts —

I. The determination of the weight of a litre of oxygen.

II. The determination of the weight of a litre of

hydrogen.

III. The ratio by volume in which these two gases

combine to form water.

IV. The synthesis of water from known weights of

hydrogen and oxygen, the weight of the water
formed being also accurately determined.

It would be impossible to give any idea of the precau-
tions taken to obtain results free from all objections in a
sketch so short as this must be, for such details the
original memoir must be consulted ; only a summary of
the results obtained can here be given.

Three methods were adopted to determine the weight
of a litre of oxygen. In the first method the barometer
and thermometer were used, and the gases weighed in
balloons holding in three of the experiments about 9 litres,
and in the other six about 21^ litres.

In the second method a globe of pure and dry hydrogen
was used as the standard for temperature and pressure, the
globe containing the oxygen having its pressure deter-
mined at the same temperature as that of the hydrogen
by means of a very sensitive differential manometer.

In the third method the globes were filled with oxygen
when they were immersed in melting ice and the pressure
accurately determined at the moment of closing. This
method had the disadvantage of wetting the surface of the
globes, and probably thereby changing their weight (although
this was duly investigated).

The values obtained by these three methods for the
weight of 1 litre of oxygen under normal conditions of
temperature and pressure at sea level in lat. 450 were

By use of thermometer and manometer- 0 = 1-42879 + "000034.
By compensation - 0=1-42887 + -000048.

By use of ice and barometer - - 0 = 1*42917 + -000048.

204 SCIENCE PROGRESS.

From various considerations taking into account errors
incidental to certain methods and liability to constant errors
Morley gives the most probable value as i "42900 ±0*000034.

In the same way experiments were made with hydrogen
and in live series but practically by three methods.

First method was practically the same as the first series
of oxygen experiments.

Second method was like the third oxygen series.

Third method utilised the power of absorbing hydrogen
possessed by palladium. The hydrogen was weighed in
the palladium and expelled into globes, and its volume and
pressure determined at the temperature of melting ice.
Series III., IV. and V. were made by this method, but
the apparatus employed varied somewhat in the various
series.

The values which result from these experiments are

Series I. Dh = -089938 gram.

Series II. Dh = '089970 gram.

Series III. Dh = -089886 + -0000049 gram.

Series IV. Dh = -089880 + -0000088 gram.

Series V. Dh = -089866 + -0000034 gram.

The higher results of Series I. and II. are possibly due to
some constant error, probably traces of mercury vapour.
The most probable value is

Dh = -089873 + 0*0000027 gram.

Part III. of the paper begins with a sketch of the methods
it was proposed to employ to determine the volumetric
composition of water. Of the three methods proposed Morley
unfortunately has only been able to carry out the one which
is the least satisfactory, viz., the determination of the
density of electrolytic gas and of the excess of hydrogen
over and above what the oxygen can unite with. Leduc
made a similar density determination, but apparently
assumed that the hydrogen and oxygen were in the exact
proportions in which they would recombine to form water.
Morley found that he always had an excess of hydrogen
when he kept his voltameter in ice and water, but that
when the temperature was allowed to rise to about 20° C.
then oxygen was in slight excess, so that no doubt at a

NOTES ON ATOMIC WEIGHTS. 205

certain temperature the gases do come off in atomic propor-
tions. In each experiment the weight of the gases given
off was about 23 grams.

The weight of a litre of the gas thus given off from
solution of soda made from clean sodium was —

°'53551Q ± o-ooooio,
and corresponds to a mixture of one volume of oxygen with
2*00357 volumes of hydrogen, but the excess of hydrogen
was found to be -ooo88 giving therefore the ratio in which
the gases combine as 1 : 2*00269.

Part IV. gives an account of experiments in which
hydrogen was weighed in palladium foil, oxygen was
weighed in a globe, these were then made to combine, and
the water produced was weighed also.

From these experiments we get the following values for
the atomic weight of oxygen : —

(1) From the ratio of hydrogen and oxygen, - - 15-8792

(2) From the ratio of hydrogen and water, - - - 15-8785

or as a mean, ------ 15879

From Parts I., II., III. of the memoir we get

1*42000 2 0

—17~ x = 15-879

•089873 2-00269

How excellent Morley's work is can perhaps best be
seen by comparing his results with the means of those of
previous experimenters,

Rayleigh's

summary. Morley.

Density of oxygen at Paris, - - 1-42961 1-42945

Density of hydrogen at Paris, - - -08991 -089901

Ratio of densities mean of all previous determinations, - - 15-9005
Ratio of densities, Morley's, 15-9002

Ratio of combining volumes, Morley, - 2*00269
„ ,, Scott, - 2*00285

,, ,, Leduc, - 2*0037 (corrected = 2 0024)

Although the results obtained by Thomsen agree
wonderfully well with those of Morley it is not because his
apparatus and his methods of working are so carefully
elaborated. On the contrary what strikes one most forcibly
is the extreme simplicity of the apparatus and mode of

206 SCIENCE PROGRESS.

working it as well as the neglect of certain precautions
which could well have been taken, and ought to have been
taken in an attempt to settle such an important constant as
the present ; such precautions as to weighing with counter-
poises of equal volume, for example, seem to have been
neglected.

The method was to determine, firstly, the weight of
hydrogen given off from unit weight of aluminium when
dissolved in strong potash solution ; secondly, by supplying
oxygen to a small combustion chamber so as to burn the
hydrogen evolved from a known weight of aluminium, and
collect all the water formed in the apparatus, one gets thus
the gain of the equivalent amount of oxygen to the hydro-
gen and to the aluminium. The only corrections not of
the simplest order were due to the oxygen and hydrogen
remaining in the apparatus or which had to be evolved after
the combustion had ceased. It was not found possible to
burn all the hydrogen evolved completely as the current
became so very slow when a very little aluminium remained
undissolved. The aluminium did not require to be perfectly
pure as long as it gave off no other gas than hydrogen. It
was found that 162 "3705 grams of aluminium gave off
1 8*1778 grams of hydrogen giving the ratio

Hydrogen

p — = 0*111902 + "000015

Aluminium

as the mean of twenty-one experiments.

The weight of oxygen required to combine with 86*9358
grains of aluminium (or rather with the hydrogen evolved
by its solution in potash) was found to be yyiSyG grams
from which we get the ratio

°*W^ = -88787 ±00001 S
Aluminium

from which two results we get

O -88787

5- = — — = 7 '9345

Ho '11190

or — = i?-86qo + "oo22
H D ~

We seem to have every reason now to regard it as com-
pletely proved that the atomic weight of oxygen is 15*87 to

NOTES ON ATOMIC WEIGHTS. 207

r 5*88 times that of hydrogen, the higher value being in all
probability the more correct.

Having now satisfactory determinations of our funda-
mental ratio we still require other ratios to be able to de-
termine conveniently the atomic weights of many elements.
If an element forms many compounds with oxygen it is
never safe to conclude without the most rigorous proof that
we have a pure oxide absolutely free from the other oxides
of the same element. Hence determinations of atomic
weights made by the reduction of oxides to the element or
of one oxide to a lower one or of the oxidation of an
element to an oxide or of one oxide to a higher oxide must
always be accepted with caution. The use of the haloid
compounds (especially those of bromine), of many elements,
is of the greatest value, and for this we require an exact
knowledge of the ratio bromine : oxygen. For this we
depend chiefly on the classical work of Stas. The publica-
tion of the complete works (5) of J. S. Stas under the able
editorship of Professor W. Spring, of Liege, enables every
one now to obtain in an elegant and convenient form these
models and masterpieces of accurate research which were
formerly so difficult to procure. How great the contrast
between the work of Stas and too much of that turned out
at the present day a glance at almost any page of his
works will show. Every step was proved most conclusively,
however simple and even axiomatic it may seem to us now,
before he proceeded to more elaborate propositions and
deductions. For instance, in his Nouvelles Recherches he
begins by proving that ammonium chloride prepared from
absolutely different sources and purified in different ways
always contains exactly the same proportion of chlorine,
and that the same weight of each sample precipitated
exactly the same amount of silver from its solution in
nitric acid. He obtained his ammonia from ordinary sal
ammoniac after destroying any organic bases by a treat-
ment with aqua regia, and from commercial ammonium
sulphate by a similar purification, by heating it to a high
temperature with strong sulphuric acid, and then oxidation
with nitric acid, and from potassium nitrite by reduction in an

2o8 SCIENCE PROGRESS.

alkaline solution with purified metallic zinc. The ammonium
chloride was sublimed now in a current of ammonia gas,
now in vacuo, but the results obtained showed that for the
complete precipitation of 100,000 parts of silver, 49,592 to
49,602 parts of ammonium chloride were required. In
other words, the extreme difference in a large number of
determinations carried out with very considerable modifica-
tions only amounted to one part in five thousand.

Having thus proved that a compound always contains
the same proportion of its constituent elements it was
essential for his purpose as well as for the complete
establishment of the atomic theory to prove that the equiva-
lent weight of an element was not affected in the slightest
degree by the various elements with which it might
combine. To take an example, silver combines with
iodine to form the iodide, and with iodine and oxygen to
form the iodate, and these compounds are represented by
the formulae Agl and Ag I03 respectively. It was just
possible, one might even say probable, that the ratio of silver
to iodine in the one compound might not be the same as
that in the other, but that it would be modified by the large
quantity of oxygen present in that other substance. If,
however, the elements consist of small particles alike in all
respects, such a variation would be impossible, and the
relative masses of silver and iodine in the iodide and in the
iodate must be absolutely the same. To prove this may
seem very easy, but Stas found it by no means so, lor
whenever he prepared his silver iodate by precipitation from
the nitrate, after the reduction with sulphurous acid there
was always a small excess of silver over and above the
iodine present. This he finally traced to a minute quantity
of the nitrate being carried down mechanically by the
iodate, but so firmly held that no amount of washing would
remove it. By using other soluble salts of silver such as
the sulphate and the dithionate, however, he was able to
prepare silver iodate so pure that on reduction to silver
iodide not the slightest trace of either silver or iodine re-
mained in excess. In the case of that prepared from the
nitrate the excess of silver only amounted to one part in

NOTES ON ATOMIC WEIGHTS. 209

3,000,000. These simple experiments give us some idea
as to how hard it is to obtain even very simple compounds
in a state of absolute purity. Having thus laid the founda-
tions for his further work, and shown that the combining
proportions of elements are mathematically exact, Stas con-
sidered no labour too great if thereby he could obtain more
accurate values for these proportions. Any work done
since his determinations has only tended to uphold his
values and to increase our admiration for his work.

The great value of very accurate experimental work
has been most strikingly exemplified by Lord Rayleigh's
determinations of the density of nitrogen (6). He
found that the nitrogen which he could obtain from air
alone by removing the oxygen was very little denser, but
was always denser than that prepared from the air with the
aid of ammonia by Harcourt's method, and that the nitro-
gen prepared from ammonia or from any compound had
always the same density, and that this was still lighter than
that partly from air and partly from ammonia. From this
he concluded that besides nitrogen the atmosphere must
contain another constituent still denser, which like nitrogen
resisted the action of iron and copper as well as their oxides,
even when very strongly heated. By combining the
nitrogen with oxygen after the method of Cavendish, or by
causing the nitrogen to unite with metallic magnesium, a
new gas to which the name of argon has been given was
finally separated by Rayleigh and Ramsay after much
laborious work. The detection in the atmosphere of a
constituent hitherto unsuspected as well as its isolation are
apparently only the first fruits of a number of more or less
startling discoveries Mowing directly from Lord Rayleigh's
very accurate work. The molecular weights of argon
(7) and helium (8) are respectively 40 and 4, and if their
molecules are monatomic this would give us the same
numbers for their atomic weights, but if the molecules are
diatomic, as is probable, these numbers would be halved for
the atomic weights. It is far from certain that either what
we call argon or what we call helium is not a mixture of
several similar substances.

210 SCIENCE PROGRESS.

Several atomic weights have been redetermined with
great care, and of these determinations perhaps those
of T. W. Richards of barium and of strontium are the most
accurate and most interesting. By an exhaustive research
on barium bromide he deduces the value Ba = 137*434
(O = 16) (9). From a similar study of barium chloride the
value Ba = 137*440 is deduced (10).

This value is notably higher than that usually accepted
and is no doubt due to the careful elimination of small
quantities of strontium and calcium which have contaminated
the preparations of earlier experimenters. From a study of
strontium bromide Richards found Sr = 87*659 (O = 16)

Still more recently the atomic weight of zinc has been
determined by Richards and Rogers again by means of the
bromide and precipitation with silver, and as a mean they
find the value (Zn = 65*404) (O = 16) (12).

In all the above determinations Richards estimated the
percentage of silver in his haloid silver salt and showed it
to be identical with that found by Stas, thus placing his
work on the same footing and guaranteeing in this way its
very high accuracy.

In 1888 two other American experimenters, Burton and
Morse (13), published the results of their work on the same
atomic weight which they arrived at by means of the con-
version of the metal into the oxide by treatment with nitric
acid and ignition of the nitrate. Although their work
agrees throughout very well the value found is lower than
that of Richards, due no doubt to the retention by the
oxide of oxides of nitrogen as Marignac pointed out. In
defending their work against this objection they expose
their want of knowledge of the commonest reactions in such
a way as to make one distrust all their work. The perusal
of their paper provides much food for reflection of a serious
nature although it does give a certain amount of instruction
as well as amusement. They carry out their weighings to
*ooooi of a gram and pretend to detect differences of this
minute amount in porcelain crucibles which have been
heated up to the melting point of steel. In their account

NOTES ON ATOMIC WEIGHTS. 211

of the purification of metallic zinc by distillation in vacuo it
is rather odd to find it stated that indiarubber tubing with
glycerine joints could not be used because the vapours of zinc
and of glycerine interact. What pressure of the vapour of
each is likely to exist at the highest temperature to which the
joints would ever be subjected ? The presence of gold in
the nitric acid distilled from a platinum still, and coming
from the gold solder used in it sounds also rather peculiar.
One knows that very finely divided gold will dissolve in
fuming nitric acid if kept cold, but one could hardly have
thought of finding it as an impurity in nitric acid prepared
by distillation. But the gem of all the statements comes at
the end of the paper when these two rising experimentalists
proceed to criticise Marignac's work (14), and finally to
teach him and us how we ought to test for oxides of nitro-
gen by means of starch and potassium iodide. After
proving to their own satisfaction by a process which cannot
reveal the presence of any of these oxides that they are
therefore obviously absent, they conclude that Marignac
was ignorant of the necessary precautions which must be
taken to exclude oxygen, especially that of keeping the
solution practically boiling so that the steam may keep out
the air. It is usually accepted as a well-established fact
that the delicacy of this reaction decreases rapidly with rise
in temperature, and that the colour goes completely before
the boiling point is reached, even in the presence of
relatively large quantities of free iodine.

Amongst other noteworthy determinations of atomic
weights made recently are those of Winkler, who finds
the values Ni = 58*91 and Co = 59*67 by means of the
reaction between the chlorides and silver (15); and still
more recently Ni = 5871 and Co = 59*37 (16) by deter-
mining the amount of iodine required to unite with the
pure metal. Winkler uses the value Ag = 107*66, if we
use O = 16 or Ag = 107*93 these last values become

Ni = 58-863
Co = 59*517

The determinations of the atomic weight of boron by

15

212 SCIENCE PROGRESS.

Ramsay and Acton (17), as well as by Rimbach (18), are
very interesting as examples of various methods of attacking
this problem, and which give fair results, but they can
hardly be said to have given results possessing greater
accuracy than those of Abrahall (19).

Of all the elements of which the atomic weights are still
in doubt, and of which the determinations are very unsatis-
factory, by far the most interesting is undoubtedly tellurium.
According to the periodic classification of the elements it
ought, as is well known, to have an atomic weight less than
that of iodine, but all the most satisfactory determinations
are irreconcilable with this, and make the atomic weight
notably higher than that of iodine. The experiments made
in recent years both by Brauner (20) and by Wills (21)
agree in this, no matter what method is adopted as long as
it is one which gives concordant results. The latest deter-
minations, those of Staudenmeier (22) which start from
telluric acid, give, according to him, the values 127*6,
127*1, and 127*3 f°r three series of experiments in which
different ratios were determined. He takes as his standard
O = 16 and H = 1*0032. Staudenmeier upholds that tel-
lurium is an element in opposition to Brauner who at one
time maintained that it was a mixture of true tellurium with
a higher homologue, but now concludes that this is very im-
probable, and since the discovery of argon suggests that
the assumed impurity may be a homologue of argon.
Speculations of this nature are strongly to be discouraged
and condemned, especially when their basis is nothing
more than the assumed abnormality in the periodic ar-
rangement of the elements coupled with a very decided
want of agreement in the results of an experimenter's own
work obtained by different methods. They may afford an
easier way out of a difficulty than by working steadily at
the causes of such discrepancies, but afford at best but a
feeble and undignified cover for one's retreat.

P.S. — About the middle of last month, and after the
above article was written, Thomsen (23) published the
results of some new determinations of the densities of
oxygen and hydrogen. The oxygen was prepared by

NOTES ON ATOMIC WEIGHTS. 213

heating a mixture of potassium chlorate and ferric oxide,
and the hydrogen from a solution of caustic potash by the
action of metallic aluminium. The values found were : —

Weight of one litre of oxygen at 0° C. and 760 mm. pressure, at
sea-level in Latitude 45° - - - = 1*42906 grams.
And of hydrogen similarly = -089947 gram.

From these he deduces the ratio of the volumes in which
they must combine to form water to be 1 : 2*00237.

BIBLIOGRAPHY.

(1) Thomsen, J. Experimentelle Untersuchungen zur Feststel-

lung des Verhaltnisses zwischen den Atomgewichten des
Sauerstoffs und Wasserstoffs. Zeitschrift fur physikalisdie
Chemie, xiii., 398, 1894.

(2) Meyer, L., und Seubert, K. Ueber das Verhaltniss der

Atomgewichte des Wasserstoffes und des Sauerstoffes.
BericJite ler deutsclien chemischen Gesellschaft, xxvii., 2770-
2773, 1894.

(3) Morley, E. W. On the Densities of Oxygen and Hydrogen,

and on the Ratio of their Atomic Weights. Smithsonian
Contributions to Knoivlcdge, No. 980, 1895.

(4) THOMSEN, J. Experimentelle Untersuchung iiber das Atom-

gewichts verhaltniss zwischen Sauerstoff und Wasserstoff.
ZeitscJirift fur anorganische CJiemie, xi., 14, 1896.

(5) STAS, J. S. Giuvres completes. Edited by Professor W.

Spring, Bruxelles, 1894.

(6) Rayleigh, Lord. On an Anomaly Encountered in Deter-

minations of the Density of Nitrogen Gas. Proceedings of
the Royal Society, lv., 340, 1 894.

(7) Rayleigh and Ramsay. Argon, a New Constituent of the

Atmosphere. Philosophical Tra?isaction±, clxxxvi., A. 223,
1895.

(8) Ramsay, W. Helium a Constituent of Certain Minerals.

Journal of the CJiemical Society, Ixvii., 684, 1895.

Langlet, N. A. Ueber das Atomgewicht des Heliums.

Zeitschrift fur anorganische Chemie, x., 289, 1895.

(9) Richards, T. W. A Revision of the Atomic Weight of

Barium ; the Analysis of Baric Bromide. Proceedings of
the American Academy of Arts and Sciences, xxviii., 1-30,
1893.

214 SCIENCE PROGRESS.

(10) RICHARDS, T. W. A Revision of the Atomic Weight of
Barium; the Analysis of Baric Chloride. Proceedings of the
American Academy of Arts and Sciences, xxix., 55-91, 1893.

(n) RICHARDS, T. W. A Revision of the Atomic Weight of
Strontium ; the Analysis of Strontic Bromide. Proceedings
of the American Academy of Arts and Sciences, xxx., 369-
389, 1894.

(12) RICHARDS, T. W. and ROGERS, E. F. Neubestimmung des

Atomgewichtes von Zink ; analyse von Zinkbromid. Zeit-
schrift fiir anorganische CJiemie, x., 1-24.

(13) Morse, H. N. and Burton, W. M. The Atomic Weight

of Zinc as Determined by the Composition of the Oxide.
American Chemical Journal, x., 31 1-32 1, 1888.

(14) Marignac,C.DE. Verification de quelques poids atomiques :

Zinc. Archives des sciences physiques et naturelles [3] x., 193,
1883.

(15) Winkler, C. Ueber die vermeintliche Zerlegbarkeit von

Nickel und Kobalt und die Atomgewichte dieser Metalle.
Zeitschrift fiir anorganische Chemie, iv., 10 and 462,
1893.

(16) Winkler, C. Die Atomgewichte von Nickel und Kobalt.

Zeitschrift fiir anorganische Chemie, viii., 291, 1895.

(17) RAMSAY, W. and ASTON, E. The Atomic Weight of

Boron. Journal of the Chemical Society, lxiii., 207, 1893.

(18) RlMBACH, E. Zum Atomgewicht des Bors. Berichte der

deutschen chemischen Gesellschaft, xxvi., 164, 1893.

(19) ABRAHALL. The Atomic Weight of Boron. Journal of the
Chemical Society, Ixi., 650-666, 1892.

(20) BRAUNER, B. Experimental Researches on the Periodic

Law. Journal of the Chemical Society, lv., 382-411, 1889.

(21) Wills, W. L. On the Atomic Weight of Tellurium. Journal

of the Chemical Society, xxxv., 704-713, 1879.

(22) Staudenmeier, L. Untersuchungen iiber das Tellur.

Zeitschrift fur anorganische Chemie, x., 189, 1895.

(23) Thomsen, J. Experimentelle Untersuchung iiber die Dichte

des Wasserstoffes und des Sauerstoffes. Zeitschrift fib
anorganische Chemie, xii., 1-1 5, 1896.

Alexander Scott.

THE STELAR THEORY; A HISTORY AND A

CRITICISM.

PART II.
THE METAMORPHOSES OF THE STELE.

IT is clear that the theory of polystely forms an
integral part of the general stelar doctrine, and we
can hardly refuse to accept its main idea. But though each
stele in the polystelic stems of, for instance, Aiiricula Ursi
and many Polypodiacea^ is clearly the equivalent of the
whole cylinder in the hypocotyl of the same plants, cases
exist in which we seem forced to consider as steles,
vascular strands which have none of the characters of the
cylinder left about them.

Deriving our idea of the typical stele from the mono-
stelic organ, we come to consider it as essentially cylindrical
and radially symmetrical. It is true that diarch roots are
bilateral in structure, and the primary root and hypocotyl of
very many ferns being diarch the steles of a great number
of their stems are likewise diarch and hence bilateral. And
this bilaterality often extends to the shape of the stele which
becomes oval or band-shaped instead of circular in transverse
section, the two protoxylems being situated at the extremi-
ties of the figure. Another step is for the stele to become
more or less semilunar in transverse section, so that it is no
longer symmetrical about the plane passing through the
protoxylems, but only about the bisecting plane perpendi-
cular to this. And further the protoxylems may lose their
symmetrical arrangement, or one only may be present, and
this may be excentrically placed (Angiopteris). We clearly
could not tell that such strands were steles if we had no
knowledge of their connexions and disposition. At least
as far as tissue arrangement goes they may often be said to
have lost those characters which entitle them to the name.
A similar difficulty meets us in the case of the vascular
strands in many fern leaves. Undoubted steles found in

216 SCIENCE PROGRESS.

the petiole, after repeated branchings gradually lose the
phloem from their upper sides, and thus come to possess the
collateral structure of the bundle of a Phanerogamic leaf.
On the other hand the curved bundle in the petiole of
Osmunda is certainly a meristele, if we may judge from its
connexion with the bulky central cylinder of the mono-
stelic stem, yet it is surrounded by a complete mantle of
phloem, and indeed conforms in structure to many true
steles (cf. 1 8). We may probably draw the same con-
clusion as to the " petiolar steles " of Gleicheniacese (19).

Similar facts appear to obtain in the polystelic genera of
Phanerogams, upon which we may expect much new light
from as yet unpublished researches. One instance is,
however, too instructive to be omitted. A number of
distinct steles arranged in a circle enter the peduncle of
Auricula Delavayi (8, p. 304), fuse laterally, and become
indistinguishable from a monostele, the central extra-stelar
tissue passing over into pith.1 Van Tieghem warns us (10,
p. 768) not to confound such a structure formed in an
essentially polystelic stem with an essentially monostelic
stem. But if this sort of thing may occur, what guarantee
have we that an "essentially monostelic" stem is really
essentially monostelic, or, for the matter of that, that an
" essentially polystelic " stem is really essentially polystelic ?
If a stele can become a collateral bundle in the course of a
shoot system, the same transformation may very well occur,
or a collateral bundle may become a stele, in the course of
descent ; at least we are quite debarred from dogmatically
drawing or denying homologies between the one and the
other. Of course we can speculate, and in some cases
claim a fair degree of probability for our speculations,
especially when we have a minute knowledge of all the
facts in the anatomy of a given group, but since it is impos-
sible to draw a sharp line between a stele and a vascular
strand that is not a stele we are clearly not on very firm
ground. There is certainly nothing to surprise us in this ;

1 A similar state of things appears to obtain in some of the Palm roots
investigated by Mr. Cormack.

THE STELA R THEORY. 217

the instructive fact is that "there's such divinity doth
hedge " a stele — indeed any morphological conception, as in
almost every fresh case to prevent for a time our realisation
of the truism that " Nature knows no sharp boundaries ".
In the stelar doctrine, we have, no doubt, a classification
that enables us to perceive a little more closely the direc-
tions along which the various types of vascular system in
the higher plants have been evolved, and that after all is
the most we can expect.

DEVELOPMENTAL EVIDENCE BEARING ON THE STATUS

OF THE STELE.

We have now to consider the developmental basis
of the stelar theory. Let us take the Phanerogams first.
It is well, as Dr. Scott (20) has already pointed out
in this journal, to draw a distinction between de-
velopment from the embryo, and development of the
various axes from their permanently embryonic grow-
ing points. It is clear, on reflection, that the former
alone is comparable to ontogenetic development in animals,
though it would be a mistake to suppose that the latter is
not of importance to morphology. In the comparatively
few types of monostelic plants with the anatomy of whose
embryos we have a sufficient acquaintance, it appears
that both in the plumule and radicle there is really a
clear separation at the apex between central cylinder
and cortex (plerome and periblem). But it is certainly
open to doubt whether this distinction, as Hanstein
thought, is really maintained at the growing points of the
various axes throughout the life of the plant. Into the
history of the differences of opinion on this point we need
not enter. The inherent difficulties of arriving at valid
conclusions from observations have been nearly as powerful
as the subjective causes which have evidently influenced
the views of the observers in creating the extraordinary
discrepancies which exist between the various accounts.

The method employed by Ludwig Koch (21 and 22),
who recognised that the state of things at the growing
point was likely to differ at different epochs of growth, and

218 SCIENCE PROGRESS.

that hence conclusions drawn from observation of a few
sections could not be final, marks a great advance on
previous work. Koch claims to have proved (22), in Syringa
and Berberis, that the single layer of cells immediately
beneath the dermatogen, i.e., the periblem of earlier ob-
servers, divides periclinally, during a period of leaf forma-
tion, across the actual apex of the shoot, thus giving rise to
three or four superposed layers of cells. It is clear that,
if this is the case, all but the uppermost of these layers
must become part of the plerome when the apex passes
back to the state of possessing a single layered periblem.
But though our author has convinced himself that this
actually happens, his figures are not decisive. Most of the
periclinal divisions which he shows in the periblem of the
Lilac (Taf. xvi.) are clearly in connexion with the forma-
tion of the leaf rudiments. In no case are such divisions
shown across the actual apex. In fig. vi. periclinal walls are
drawn in two periblem cells removed by one cell from
the cell-group obviously concerned in the formation of a
leaf rudiment, but these walls are also removed by one
or two cells from the centre of the flat growing point,
and considering how much this free surface is encroached
upon by the developing- leaves {cf. fig. vii.) it is not
at all clear that the periclinal wall in question is not
precociously formed in a cell which will later be involved in
the base of the leaf. Yet this single periclinal wall is
really the sole evidence obtainable from his figures of the
truth of Koch's view. Nevertheless the thorough method
of investigation inaugurated by Koch must sooner or
later settle the point. For the present we must admit
that though Hanstein's case is made out for a certain small
number of plants, the great majority of cases which have
been investigated must remain doubtful. Van Tiegfhem
(10, p. 776) does not definitely commit himself, though he
implies the suggestion that Hanstein's three initial layers
are universal in Phanerogams, though often not distinguish-
able owing to " enchevetrement" of the layers. But his
pupil Douliot (23) concluded that there was a single apical
cell in all Gymnosperms, and a plero- periblem in most

THE STELA R THEORY. 219

monocotyledons and some dicotyledons, while Koch takes
the view that there is a generalised meristem without
separate layers in Gymnosperms (21) and that only the
dermatogen is separate in most Angiosperms (22). So
that the "triple layer" theory of Hanstein and Van
Tieghem is accepted by neither of these two most recent
investigators as of general application, widely divergent as
are their views inter se. Considering that the theory of
the direction of ontogeny by the separation of different
kinds of somatic idioplasm is now generally discredited, it
is difficult to see what we gain by an adherence to the un-
proved hypothesis of the strict separation of the initial
layers, even if it is still a possible hypothesis.

In the root apex on the contrary the plerome is in the
great majority of cases sharply separated from the peri-
blem, but even this rule is not universal. The sharp
separation seems to be correlated both in root and stem
with the formation of a slender compact cylinder.

In Vascular Cryptogams, which nearly all possess either
a single apical cell or a single layer of initial cells giving
rise to the whole of the tissue of the axis, there is of course
no question of a separation, at the apex itself, of initial
layers.

The separation of the young cylinder behind the actual
growing point is quite a distinct question from its separation
at the apex. It is during the development of the cylinder
that we get, usually at least, a distinct limit between it and
the cortex which is often lost in the adult stem, and this is
a point of great importance.

Long before the stelar theory was originated, most of
the great anatomists, who laid the foundations of our know-
ledge of the histology of vascular plants, were practically
agreed on the generality of this early separation. This is
clearly shown in the terminology employed in designating
the various regions.

Thus Sanio (24), tracing from the apex the development
of the various tissues, showed that in many cases the young
pith first became separated from an outer zone, and that
in the latter the "thickening ring" (really corresponding to

220 SCIENCE PROGRESS.

Flot's "vascular meristem," i.e., the ring of tissue produc-
ing the bundle system plus the "external conjunctive":
shortly became differentiated from the peripheral zone or
young cortex. In other cases {Euonymus and Berberis),
the "thickening ring" appeared or began to appear before
the young pith became separated from the " outer zone".
Hanstein (25), as a consequence of his separation of the
primary meristem into Dermatogen, Periblem and Plerome,
makes the outer limit of the young cylinder, i.e., that
between periblem and plerome, of primary rank. Russow's
scheme (26), on the other hand, drawn from instances like
those of Sanio's first group,1 in which the young pith is the
first tissue to become apparent, divides the young tissue
produced by the general Protomeristem at the apex itself
into Endistem (Sanio's young pith) and Existent (Sanio's
" Aussenschicht "), the latter being separated into Mesistem
(Sanio's "thickening ring ") and Peristem or young cortex.
Thus the limit between "Mesistem" and "Peristem' is
reduced to secondary rank. But De Bary (14, pp. 395-6)
again sums up clearly in favour of the individuality of the
plerome.2 As a matter of fact the young pith often does

1 Russow placed Hanstein's best instances, for example, stem of Hip-
puris, and Roots, where there is a well-defined plerome at the apex itself,
under the separate heading of "Axes with Combined Bundles ".

2 The development of the pericycle is of great importance in this
connexion. Sanio (24) showed in several cases that what we now call the
pericycle was developed from the outer edge of the "thickening ring".
Schmitz (27) confirmed this view in Berberis and Menispermum. Van Tieg-
hem, however (5), based his conception of the pericycle entirely on the
ground of adult comparative anatomy. This is explicitly stated (p. 152) in
a remark he made at the close of a " Note sur le pericycle," read by
D'Arbaumont (28) to the Botanical Society of France. D'Arbaumont had
endeavoured to show that the sclerised portions of the pericycle, capping
the phloems of the stem bundles in dicotyledons, were developed in
common with the bundles themselves from the desmogen strands, and
were thus often separate from the interfascicular pericycle. His account
of the development of the continuous zone of fibres in Cucurbitacese and in
Berberis is different, and indicates differences in the origin of the pericycle
in various plants. It is unfortunate that no figures are given. Morot re-
plied (29) that even if the pericycle, or parts of it, were developed dif-
ferently in different plants, that made no difference to the validity or applica-

THE STELA R THEORY. 221

become recognisable in comparatively bulky apices (owing
to the early ceasing of longitudinal divisions, and the stretch-
ing of its cells), before the outer limit of the young cylinder
is defined. On the other hand, in the slender stems of
many water plants, Hanstein's scheme applies with dia-
grammatic precision, the outer limit of the cylinder being
clearly marked at the apex, before there is any sign of a
differentiation between pith and bundle ring. But these
differences of precocity in the development of the various
regions of the cylinder, depending, as they do, upon the
subsequent duration and size relations of the regions are
clearly of little importance to morphology. The important
fact which remains is the clear separation, slightly sooner,
or slightly later, of the young cylinder from the cortex, in
at any rate the vast majority of cases.

The separation thus made in development is, as a rule,
more or less clearly maintained in the adult stem, though
sometimes it is lost altogether. There is the possibility
of a complete loss of a visible boundary between cylinder
and cortex by the occurrence of irregular cell divisions in
the young pericycle and inner cortex, together with a
"shifting" (Verschiebung) of the original walls separating
the two ; unfortunately we do not know if this takes place
in some cases or not. But apart from such an occurrence
the distinction between cylinder and cortex, once made, is
always made, and the layer of cells which once abutted on
the young cylinder is still the phloeoterma, not merely
"theoretically," but in substance and in fact, however im-
possible it may become to distinguish it from the surround-
ing tissue.

It is these facts which form the real developmental basis
of the stelar theory.

The phenomena (supposing them to be established) of
real importance in the opposite sense, would be the occur-
rence of stems in which the external limit of the cylinder is
never clear, of stems, in a word, which never possess a

tion of the term. The further pursuit of the theoretical implications of this
statement would lead us into very deep waters, but it is clear that an ex-
tended comparative investigation of the origin of the pericycle is needed.

222 SCIENCE PROGRESS.

cylinder as such. While we could not admit that the stelar
doctrine applied to such stems, we should probably be
forced to the conclusion if their vascular system conformed in
all other respects to the monostelic type, that the plants in
question were derived from truly monostelic ancestors, whose
descendants had lost the limit between cortex and cylinder.

The Nymphseaceae, many of whose stems contain a
large number of "scattered" bundles, seem to furnish us
with examples of such plants. Caspary (27) states that
the bundles are here developed in centripetal order : this
would seem to indicate an analogy with those plants
(Piperaceae, Begoniacese, etc.), which possess a proper
bundle ring" and also younger bundles in the pith, rather
than with the monocotyledonous type. In at least one
member of the family, Victoria regia, which possesses
a particularly large number of these "scattered" bundles,
it appears that no well-defined cylinder is visible anywhere
in the stem.1 So here if anywhere we seem to have a real
case of "astely". We cannot, however, say the same
with certainty of any dicotyledonous stem with a single
ring of bundles. Nageli's observations (28) indeed led him
to the conclusion that the " cambial " strands were, as
a rule, developed in the midst of a homogeneous ground
tissue, but his conclusions, as we have seen, have been
negatived by most subsequent observers.

Turning to the vascular cryptogams we find that
whether monostelic or polystelic, the stele or steles can be
traced nearly up to the stem apex. The first formed peri-
clinal walls do not indeed necessarily mark the limit of
stelar tissue. They may cut off the pith, as in Equisetum
or mark the middle of the cortex, as in many roots, or
the outer limit of the ring of steles, as in many fern stems,
or of the single cylinder, as in the stolon of Nephrodium
(10, pp. 692 and 773-4). Clearly no special importance
can be attached to these walls, and we certainly can-
not use the fact that they mark off the pith in Equisetum,

1 1 owe this information to the kindness of a friend in telling me the
results of some unpublished observations.

THE STELAR THEORY. 223

as Van Tieghem does, to support the view that the genus
is really astelic. This argument depends on the assump-
tion that these walls always separate stelar from extra-
stelar tissue, which is not a fact, according to Van
Tieghem himself (10, p. 774), and further, a similar line of
reasoning would tend to show that the stems of a great
many dicotyledons, namely, those in which the pith is the
first tissue to be marked off, are also astelic.

SUMMARY OF RESULTS.

We have attempted in the foregoing pages to ex-
hibit, as clearly as possible, the bearing of well ascer-
tained facts of anatomy and development upon the stelar
theory as developed by Van Tieghem and his pupils. We
may appropriately conclude with an attempt to summarise
the results to which we are thus led.

We recognise in the central cylinder of the axes of the
great majority of the higher plants an anatomical region of
the first rank to be co-ordinated with the other great
anatomical regions, the cortex and the epidermis. The
central cylinder consists of vascular tissue (xylem and
phloem) and conjunctive tissue (typically parenchyma).
In the bulky typical * cylinder the vascular tissue is separ-
able into distinct strands corresponding with its centres (or
rather lines) of development, and giving to the cylinder a
radial symmetry ; the conjunctive of such a cylinder is
separable into distinct regions. Typically, also, the inner-
most layer of cortex, which abuts on the cylinder is dis-
tinguished by special characters.

Reduced central cylinders are found in various stem
structures, especially the thin stems of water plants. The
reduction acts first on the conjunctive, which may (though
rarely) quite disappear. This leads to the coalescence of
the strands of vascular tissue into a more or less solid
cylinder. Such a reduced cylinder is always sharply marked
of! from the cortex.

On the other hand we have stems in which it is im-
possible to separate the conjunctive from the adjacent

1 In Sach's sense of " most highly developed ".

224 SCIENCE PROGRESS.

cortical tissue. When this is the case in the adult, it is still
often possible to make the separation in the young stem.

Naming the central cylinder a stele, we call all stems
with a single cylinder monostelic.

Stems in which we cannot make the separation in any
part, and which are therefore not strictly monostelic, yet
conform more or less to the monostelic structure in other
respects, and are no doubt usually derived in descent from
the monostelic type.

Most Ferns and Selaginellas, and two genera of
Phanerogams, while showing a monostelic structure in
their hypocotyls, possess in their later formed stems more
than one cylinder, each comparable in structure to the single
stele of the hypocotyl. Such stems are known as polystelic.
The steles of a polystelic stem may, however, take on the
most various forms, and lose all the characters of the
original cylinder ; several may even coalesce to form a
structure indistinguishable from a single stele. As this, or
indeed the converse case of a non-stelar vascular strand
assuming the characters of a stele, may have happened in
descent without leaving any traces of the transformation, we
are not justified in asserting the homology of all steles or
denying homology between steles and non-stelar vascular
strands. Nevertheless the stele is undoubtedly a real and re-
latively stable type in the arrangement of vascular tissue, and
hence the name represents a real morphological conception.

The vascular tissue of a leaf is arranged in one or more
strands, each of which, bilaterally rather than radially
symmetrical, is called a schistostele or meristele, representing,
as it does, a part only of the stem cylinder. The meristele
of a petiole may, however, simulate a stele. In most poly-
stelic stems one or more of the stem steles directly enters
the petiole, and the branches maintain more or less of the
stelar character till near their endings in the lamina, where
they become indistinguishable from collateral bundles.

We are probably justified in supposing the monostelic
type to be primitive in vascular plants, and we may assume
the original stele to have been relatively simple. To the
increase in bulk of the stem and correlated increasing de-

THE STELA R THEORY. 225

mands for the supply of vascular tissue to leaves, the plant
either responded by increasing the bulk of the stele and
multiplying the number of its vascular strands, or by sub-
stituting a number of simple steles for the original single
one. This last occurrence happened once at least in the
Pteridophyta (probably more often), and more than once
among the Phanerogams.

The primordial stele is represented at the present day
by the single sharply defined stele of the embryo, which is
maintained in the root and hypocotyl, and which passes over
in the stem to one of the modern types of structure,
necessary to the various demands of the leafy shoot. The
arrangements at the apex of the latter are naturally adapted
to form the particular type of structure in question, and
can in no case be considered as representing an ancestral
form.

BIBLIOGRAPHY.

(1) Ph. van Tieghem. Recherches sur la symetrie de structure

des plantes vasculaires. Introduction, pp. 5-29. La Racine,
pp. 30-314. Annates des Sciences Naturelles, Botanique, 5
ser., tome xiii., 1870-71.

(2) Van Tieghem. Memoire sur les canaux secreteurs des

plantes. Ann. Set. Nat. Bot., 5 ser., tome xvi., 1872.

(3) FALKENBERG. VergleicJiende Untersuchnngen fiber d. Ban d.

der Vegctationsorgane d. Monocotyledonen. Stuttgart. 1876.

(4) MANGIN. Origine et Insertion des racines adventives. Ann.

Set. Nat. Bot., 6 ser., tome, xvi., 1882.

(5) VAN TIEGHEM. Sur quelques points de l'anatomie des Cucur-

bitacees, p. 277. Bulletin de la Societe" Botanique de Fratice,
tome xxix., 1882.

(6) Morot. Recherches sur le pericycle. Ann. Sci. Nat. Bot., 1884.

(7) Van Tieghem et Douliot. (a) Structure de la tige des

Primeveres nouvelles du Yun-nan, p. 95. (b) Groupement
des Primeveres d'apres la structure de leur tige, p. 126. (c)
Sur les tiges a plusieurs cylindres centraux, p. 213. Bull.
Soc. Bot. France, tome xxxiii., 1886.

(8) Van Tieghem et Douliot. Sur la polystelie. Ann. Sci.

Nat. Bot., 7 ser., tome iii., 1886.

(9) Leclerc du Sablon. Recherches sur la formation de la tige

des Fougeres. Ann. Sci. Nat. Bot., 7 ser,, tome xi., 1890.

(10) Van Tieghem. Traite de Botanique, 2ieme edition, 1888-91.

226 SCIENCE PROGRESS.

(il) FLOT. Recherches sur la zone perimedullaire. Ann. Sci.
Nat. Bot., 7 ser., tome xviii., 1893.

(12) VAN TlEGHEM. Remarques sur la structure de la tige des

Preles. Journal de Botauiqne,tome iv., p. 365, November, 1 890.

(13) Van TlEGHEM. Remarques sur la structure de la tige des Ophio-

glossees. Journ. de Bot., tome iv., p. 405, December, 1890.

(14) De Bary. Vergleichende Anatomie der Vegetationsorgane

der Gefasspflanzen, 1877 (English edition, 1884).

(15) STRASBURGER. Ueber den Bau und die Vorrichtungen der

Leitungsbahnen in den Pflanzen. Histologische Beitrage iii.,
1891.

(16) VAN TlEGHEM. Pericycle et Peridesme. Journ. de Bot.,

tome iv., p. 433, December, 1890

(17) Van TlEGHEM. Sur la structure primaire et les affinites des

Pins. Journ. de Bot., tome v., p. 265, etc., August, 1891.

(18) PAUL Zenetti. Das Leitungssystem im Stamm von

Osmunda regalis L. und dessen Uebergang in den Blattstiel.
Botanische Zeitung, April, 1895.

(19) Poikault. Recherches anatomiques sur les Cryptogames

vasculaires. Ann. Sci. Nat. Bot., 7 ser., tome xviii., 1893.

(20) D. H. Scott. Recent work on the Morphology of Tissues

in the Higher Plants. "Science PROGRESS," vol. i.,
August, 1894.

(21) L. KOCH. Ueber Bau und Wachsthum der Sprossspitze der

Phanerogamen. Pringsheinis Jahrbiicher f. zvissenschaftliche
Botanik, Bd. xxii., 1891.

(22) L.KOCH. Die vegetative Verzweigung der hoheren Gewachse.

Pr.J., Bd. xxv., 1893.

(23) DOULIOT. Recherches sur la croissance terminale de la tige

des Phanerogames. Ann. Sci. Nat. Bot., 7 ser., tome xi., 1890.

(24) San IO. Vergleichende Untersuchungen iiber die Zusam-

mensetzung des Holzkorpers. Bot. Zeit., 1863.

(25) Hanstein. Die Scheitelzellgruppe, 1868.

(26) Russow. Vergleichende Untersuchungen betreffend die

Histologic . . . der Leitbiindel-Kryptogamen, u. s. w.
Memoires de V academic imperiale des Sciences de St. Pcters-
bourgi 7 ser., tome xix., 1872.

(27) Schmitz. Ueber die Entwicklung d. Sprossspitze d. Phanero-

gamen. Halle. 1874.

(28) D'Arbaumont. Note sur le pericycle. Bull. Soc. Bot. de

France, tome xxxiii., p. 141, 1886.

(29) Morot. Reponse a la note de M. D'Arbaumont sur le

pericycle, ibid., p. 203.

(30) Nageli. Beitrage zur tvissenschaftliche Botanik, i., 1858.

A. G. Tansley.

THE PRESENT POSITION OF THE CELL-
THEORY.

PART II.

SINCE I have shown that protoplasm in the simplest
form in which it is known to us may not be regarded
as having an organisation in the sense in which that term
has any meaning, and since it is a waste of time to discuss
the use of the term when it has no meaning, we may more
profitably turn to the question whether protoplasm has a
structure, and if so, what kind of structure? Is it essenti-
ally the same in all the kinds of protoplasm which have
been studied, and is it of the same kind as the structure of
tissues and organs of metazoa or is it of a different kind ?
For it must be insisted upon that one may deny to proto-
plasm an organisation, in the proper sense of the term, and
yet one may consistently attribute to it a structure, even a
very complex structure. But that structure need not be
called an organisation, to do so is to confuse two clear
issues. It is worth while to emphasise this point, for some
people think it very inconsistent to affirm that protoplasm
has a complex structure and at the same time to deny that
it is organised.

I conceive that the view that protoplasm is composed of
granules, which are either biophors or secondary aggregates
of biophors, has been sufficiently refuted by Butschli's re-
searches on hyaline protoplasm already referred to. The
hyaline pseudopodia of Gromia show no trace of granules,
not because the granules are too small to be seen, for the
highest powers of the microscope reveal in the protoplasm,
at the moment of its protrusion to form a pseudopodium, a
structure which is not granular, namely, an alveolar structure,
and if granules were present they must necessarily be sought
for in the alveoli or in the alveolar walls. But they are to
be found in neither, so it may be affirmed that in the
simplest form of protoplasm there are no granules, a

circumstance which deprives the theory of biophors of much

16

228 SCIENCE PROGRESS.

of its weight. Of course it may be objected that the
alveolar walls and contents may be composed of biophors
so small as to defy detection ; such an objection must be
defended on theoretical grounds, and I will deal with it
presently ; just now I will confine myself to the considera-
tion of the visible structure of protoplasm.

After rejecting the granular theory we have a choice of
several others ; the fibrillar theory, the reticular theory, and
the alveolar theory of Biitschli. It would take too long for
me to examine these several theories in detail ; it has
already been done by Biitschli (loc. ciL, p. 177), and still
more recently by Yves Delage,1 if I were to undertake the
task I should only give a resume of their arguments.
For my own part I am strongly inclined in favour of Biit-
schli's " Wabenlehre ".

For some reason or other Biitschli's account of the
structure of protoplasm has not, to use a common ex-
pression, " caught on ". Possibly because it was published
at a time when men's minds were occupied with the more
alluring prospect offered by the granular theory of proto-
plasm, with all its delusive hopes of an explanation by means
of biophors, and primary organisation of the phenomena
of heredity, and of all the vital processes. Possibly also
because Biitschli himself pushed the analogy between micro-
scopic foams and protoplasmic structure too far. But if
his theoretical considerations are put aside, there is a great
deal to be said for his fundamental views. The alveolar
structure which he describes may be demonstrated in many
various forms of protoplasm. It is particularly obvious in
Pelomyxa, in which form the larger vacuoles serve admir-
ably as a contrast between the finer alveolar structure which
he claims to be common to all protoplasm and the grosser
vacuolar structure which is often mistaken for it. I have
myself identified the alveolar structure in a considerable
variety of protozoa, and in a number of tissue cells, and I
have succeeded in making Biitschli's artificial amoebae, and am

1 Yves Delage, La Structure du Protoplasma et les Theories sur
V Heredite et les grands problems de la Biologie generate. Paris : C.
Reinevald et Cie, 1895.

THE PRESENT POSITION OF CELL-THEORY. 229

convinced of the close analogy in structure between the
artifact and the natural product. The resemblance between
the two is exact, and it is astonishing. The optical char-
acters of the artificial product are explained, on physical
grounds, as the outcome of a certain structure, namely, an
alveolar structure. The identical optical characters of pro-
toplasm may surely be explained on the same grounds. It
is not pushing analogy too far to say that identical optical
characters are the result of identity of structure. The
analogy is somewhat strained when it is sought to prove
that the identity of the streaming movements in the arti-
ficial product with those in protoplasm are attributable to
the same physical causes. The chemical constitution of
the. two bodies is so different that the phenomena observed
might be regarded as secondary. Nor is the identity
absolute, for Biitschli himself points out that the induced
currents in the surrounding medium take place in the re-
verse sense in an amoeba to what they do in the case of
the microscopic foam. I cannot think that the criticism of O.
Hertwig invalidates Biitschli's theory seriously. Hertwig
says that lamellae of oil consist of a fluid which is not
miscible with water. If the comparison between the
structure of an emulsion and the structure of protoplasm
depends on something more than a superficial resemblance,
then the lamellae of plasma which are compared with the
lamellae of oil must consist of a solution of albumen
or of a fluid albumen. But a solution of albumen is
miscible with water, and therefore it would mix with the
contents of the alveoli : emulsions of albumen must be formed
with air, not with water. To this Biitschli answered that
the framework of plasma consists of a fluid composed of a
combination of an albumen and a fatty acid, which was
therefore not miscible in water. Another obvious answer
is that living plasma is not a simple albuminous solution,
for if it were most protozoa could not exist, they would
immediately dissolve in the water in which they live.
Whether a fatty acid exists in combination with the plasma
or not, there is something in the constitution of living-
plasma which differentiates it from albumen, for it does not

23o SCIENCE PROGRESS.

dissolve in water ; dead plasma on the other hand becomes
albumen and dissolves speedily. What that something is
I do not venture to suggest ; could we ascertain what it is,
no doubt we should have discovered the solution to the
riddle of life. Hertwig says that the structural elements of
protoplasm, be they filaments, or reticular, or lamellae, or
alveoli, or granules, or what else, have a fixed state of
aggregation. Protoplasm is no mixture of two immiscible
substances such as water and oil, but consists of a union of
fixed organic material particles with abundant water. This
is but a verbal statement of the facts and is no explanation,
but he adopts later on {Joe. tit., p. 49) Nageli's micellar
theory as an explanation. No doubt it is the best explana-
tion possible, but it again does not give more than a verbal
explanation of the remarkable and fundamental phenomenon
that protoplasm, be its structure what it may, does not when
alive dissolve in water, but when dead it becomes some-
thing else which readily dissolves, provided of course that it
is not killed by means which coagulate the albumens into
which it is converted at death.

I shall recur again to the micellar theory, for the pre-
sent purpose it is sufficient to say that it is not inconsistent
with Biitschli's " Wabenlehre,"1 and might even be pressed
into service to explain why the plasma does not mix with
the watery alveolar contents without the necessity of calling
fatty acids to aid.

Supported by these considerations, and by a considerable
mass of objective evidence, I venture to think that Btitschli

1 Biitschli criticises the micellar theory and the analogous theory of
"inotagmas" put forth by Engelmann. He does not accept either, but
does not give in their place any theory of the ultimate compositions of the
substances which form the alveolar framework and contents, except that
(p. 309) he says, " a series of reflections . . . led me to suppose . . . that
the chemical basis of the framework substance must be formed by a body
which has arisen from a combination of albuminoid and fatty acid mole-
cules." Such a combination must mean the formation of a chemical unit
of a higher order than the molecules which enter into its composition, and
for my purposes such a chemical unit is a micella. In this limited sense
the acceptance of a micellar structure is not incongruous with the " Wa-
benlehre ".

THE PRESENT POSITION OF CELL-THEORY. 231

has given a true account of the minute structure of proto-
plasm, so far as it can at present be determined by optical
means. And I even venture to prophecy that when the
history of the biological work of this half century comes to
be written some half century hence, the theories of biophors
and plasomes and the such like will have merely a historical
interest, whilst the work of Biitschli will be regarded as the
most sagacious and far-sighted contribution of our time to
this momentous question. In saying this I do not wish
to declare my adhesion to the more theoretical part of
Biitschlis work, but only to his account of the microscopic
structure of protoplasm.

Even if one were to accept his explanation of the
streaming movements there would remain all the other
phenomena of life to be accounted for, and they are inex-
plicable on the visible structure of protoplasm, even if it be
an alveolar structure.

Underlying the visible structure then there must be an
invisible structure, which is the cause of the phenomena.
This admission once made, the claims of the rival theories
of biophors, plasomes, plastidules and what not, again press
themselves on our attention. Now it is to be remarked
that the most cautious and thoughtful theorists do not claim
that their hypothetical units are an explanation of life.
Weismann categorically denies that his theory of the germ
plasm is a theory of life, it is only a theory of heredity, but
he goes so far as to suggest that a workable explanation of
the more complicated vital phenomena may be the surest
indication of the path which will lead to an explanation of
the more simple (loc. ciL, p. 21).

Others, however, are not so cautious, and in any case
there is this feature common to all, that they aver on the
one hand that vital processes are so complicated that they
cannot be explained by a physico-chemical theory of the
constitution of protoplasm, and that therefore we must
assume the existence of ultimate vital units or biophors :
on the other hand, after endowing these biophors with all
the attributes of life, they say that they have a comparatively
simple molecular constitution upon which the phenomena

232 SCIENCE PROGRESS.

which they exhibit depend. In fact they describe essenti-
ally similar functions in biophors and in cells, but they
allow a physico-chemical explanation in one case and
disallow it in the other. This contradiction has been
noticed by others, and it has never been satisfactorily
explained away. Whitman draws attention to it, and
observes that no one, as far as he knows, has looked upon
the unit as anything more than the seat of the mystery.
This is true, but it is no reason for putting" the mystery in
a small bag instead of a big one. He defends the theories
of smaller units, however, by saying that they have ex-
tended our knowledge of organic mechanism {Joe. cit.,
prefatory note, p. vi.). This again I believe to be true,
but not quite in the sense in which Whitman apparently
means it to be. The theories of minute independent vital
units have, I believe, led many on the wrong track as
regards vital mechanism ; the attacks on such theories are
leading to a considerable extension of our knowledge in
this direction. The ultimate vital units confessedly do not
remove the mystery ; ultimately the explanation of life
must be a chemico-physical one ; there is no alternative
but a vitalistic theory, and this is not admissible in science.
The strongest ground, viz., the granular hypothesis, for
assuming the presence of vital units is removed by the
observed constitution of hyaline protoplasm, and finally
none of the assumed aggregates of units which are admitted
to be visible, are identified with various sorts of granules
and considered to constitute units of a higher order, have
ever been shown to be capable of leading an independent
existence.

On the other hand there is a oeneral consensus of
opinion that protoplasm is not a simple organic compound.
Its unit is not the molecule, but an aggregate of molecules
forming a unit of a higher order to which the molecule
stands in the same relation as the atom does to the mole-
cule. It is also admitted that these molecular aggregates
may exist in many different kinds in protoplasm. Such a
conception is absolutely necessary for the explanation of
the most simple properties of organic bodies, for example,

THE PRESENT POSITION OF CELL-THEORY. 233

their optical properties and the imbibition of water. But it
is a physico-chemical conception, and the molecular aggre-
gate need not and should not be endowed with independent
vital powers. Such a molecular aggregate is the micella.
In accepting the micella one may attribute any amount of
complexity to protoplasmic structure without for a moment
admitting that it is a cono-eries of elementary organisms.
Nor need we admit all the theories which Nageli has tried
to establish as the necessary consequences of the assumption
that there are such things as combinations of polyatomic
molecules into groups of a higher order. As I have already
said, it was pointed out by von Sachs that even in the
region of pure chemistry it is necessary to assume that polya-
tomic molecules are grouped into closer molecular unions,
thus giving rise to chemical properties which did not belong-
to the individual molecules. But in the region of pure
chemistry such a grouping is not called an organisation,
nor is there any reason why it should be called an organisa-
tion in the present case. Let us be perfectly definite and
say that by a micella we mean a combination of polyatomic
molecules into closer union to form a group ; nothing more,
except in so far as we may reason on chemico-physical
grounds as to the behaviour of such groups and their
relations inter se. For instance (I am quoting from O.
Hertwig's summary of this part of the micellar theory) :
"The micellae exert an attraction both on water and on one
another, whereby the phenomena of swelling may be ex-
explained. In a dry organic body the micellae lie close to
one another, separated only by exiguous envelopes of
water : these latter enlarge considerably during imbibition,
since the attractive forces between the micellae and water
are at first greater than between the micellae themselves.
The micellae are separated from one another by the imbibed
water as it were by a wedge ; but an organised body does not
arrive at a condition of solution, since the attraction of the
micellae for water diminishes in the course of their separa-
tion from one another, at a greater rate than the attraction
of the micellae for one another, and therefore, when the
watery envelopes have attained a certain size, a condition

234 SCIENCE PROGRESS.

of equilibrium, the limit of imbibition is reached." And
also: "Since particles of water may be held fast on the
surfaces of the micellae by molecular attraction, so also
other matters (lime and siliceous salts, colouring matters,
gelatin compounds, etc.) may be deposited on them after
they have been taken into the organic body in a state of
solution ". So far as my physical knowledge enables me to
form a judgment, attributes such as these may justifiably be
ascribed to micellse on purely physical grounds and their
importance can hardly be overestimated, since the last
passage quoted affords a hint as to the nature of the essen-
tially vital process of assimilation. It is not my business
now to develop a complete theory ; I doubt indeed whether
a complete theory is possible in the present state of our
knowledge. I have done sufficient for present purposes if
I have succeeded in indicating what ideas we may justifiably
hold on the subject of protoplasmic structure, and I believe
that I have given some good grounds for justification of the
views that ; (i) the ultimate visible structure of protoplasm
is an alveolar structure ; (2) that the invisible structure of
protoplasm is a "micellar" structure in the sense defined
above.

But before I proceed I must enter a caveat against
being considered as an adherent of the micellar theory of
Nageli. I cannot enter here into my reasons, but I may
say that the further theories which Nageli assumes to
be the necessary consequences of the existence of micellae,
do not appear to me to be necessary consequences at all ;
indeed I part company with him at once when I express my
conviction that the hypothesis of a micellar structure is
compatible with the alveolar structure described by
Butschli.1

1 Since the above argument was first written out the work of Yves
Delage has come into my hands. It is most gratifying to find that the
opinions of so distinguished an author accord so exactly with my own. The
reader who finds my argument involved and laborious may turn with profit
to Delage's book, in which he will find a lucidity of expression and a
precision in argument which I can only envy without hoping to imitate. It
is worth while quoting the following passages here: "On peut accorder

THE PRESENT POSITION OF CELL-THEORY. 235

I may now anticipate the objection which is certain to
be raised that the visible and invisible structure which I
assign to protoplasm is utterly inadequate to explain the
phenomena of life. It is inadequate and it is intended to
be inadequate. Were I to pretend that it is adequate I
should be running counter to all the lessons taught by our
experience of living things. The structure which I have
assigned to protoplasm applies particularly to that simplest
known form of it which we rarely meet with, but which we
do meet with in exceptional cases, for instance in the pseudo-
podia of Gromia dujardini. But separate a protoplasmic
corpuscle formed by the thickenings of the thread-like pseu-
dopodia of this species from the rest of the animal ; the cor-
puscle separated is not any longer capable of an indepen-
dent existence, it soon perishes, it has all the structure
which I have described, but it is not capable of in-
dependent life. Clearly then life is not the outcome of this
structure, though the structure may play its part, and no
unimportant part in the life processes.

When I have been speaking of protoplasm I have
obviously been confining my attention to that form of it
which is now generally distinguished under the name of
Cytoplasm. Cytoplasm taken by itself is not living matter
in the sense that it is capable by itself of maintaining an
independent existence. The experiments of Nussbaum,1 of
A. Gruber and Verworn, confirmed by other observers, have

a l'auteur (Nageli) ses Micelles. Leur constitution, leurs proprietes n'ont
rien que de tres admissible. Bien que leur mode de generation ne soit
guere probable, il n'y a aucune raison positive pour le repousser. Mais
l'arrangement des micelles et la structure de l'idioplasma sont invraisem-
blables au plus haut point. Nous avons demontre, au cours de notre
expose, que cet arrangement n'est pas de tout, com me l'auteur l'avance, le
resultat necessaire du seul jeu des forces moleculaires initiates ce n'est
qu'a grand renfort d' hypotheses etagees l'un sur les autres qu'il arrive a
faire disposer les Micelles en Files, les Files en Faisceaux, les Faisceaux en
Cordons et les Cordons en un Reseau repandu dans tout l'organisme."

1 It was Nussbaum who first introduced the method of dividing in-
fusoria by artificial means, and the credit of having devised this very useful
class of experiment belongs to him. In my previous article I inadvertently
assign it to Gruber.

236 SCIENCE PROGRESS.

shown that pieces of cytoplasm cut off from the remainder
of a protozoon are incapable of maintaining life and soon
perish. If, on the other hand, a fragment of cytoplasm
similarly cut off contains nuclear matter, it is shown to con-
tain the attributes necessary to life, for the fragment does
not perish but reconstitutes itself and becomes an inde-
dependent living being. The converse also holds good.
A nucleus or a fragment of a nucleus isolated from a
protozoon, is incapable of life and perishes. But a nucleus
or a fragment of a nucleus in conjunction with a fragment
of cytoplasm is capable of life and constitutes an indepen-
dent living being. The reasonable inference is that cyto-
plasm plus nuclear matter is indispensable for the per-
formance of vital functions.

Now cytoplasm plus nuclear matter constitutes a cell.

I have elsewhere discussed at some length the definition
of a cell,1 and I have defined it as a corpuscle of protoplasm
which contains nuclein. In the present state of our know-
ledge this definition seems the only one possible. The cell
then consists of two essential substances, cytoplasm and a
substance which is different from cytoplasm, both structurally
and in chemical constitution, namely, nuclein. In a great
majority of cells other substances are present which are
different from both of these. Such substances are the
centrosomes, that modification of cytoplasm which is called
archoplasm, amylum and aleurone grains and so forth. As
far as we know, however, these substances are not essential
to life, but are secondary products characteristic of dif-
ferentiated cells. Recent researches on the structure of
Bacteria and Oscillaria justify the assertion that cells exist
in which these substances are absent. We know next to
nothing about the presence or absence of centrosomes and
archoplasm in the Protozoa, and it may be that further
investigation will lead us to the conviction that these two
are as essential to the life of these forms as the presence of
cytoplasm and nuclein. Maybe not ; in any case it does

1 Quarterly Journal of Microscopical Science, vol. xxxviii., p. 137,
1895.

THE PRESENT POSITION OF CELL-THEORY. 237

not matter for present purposes. It is sufficient to know
that two substances, cytoplasm and nuclein, must be brought
together or life cannot exist, and that it does exist in
organisms in which these substances, and these only, can be
detected, viz., in Bacteria. This statement may appear some-
what hazardous, seeing that the presence of a nucleus is
denied in several living beings, in bacteria, for instance, and
in yeast. A nucleus in the sense of a centralised body is
certainly absent in these and in many other forms, but
Biitschli has demonstrated the presence of nuclein in
Oscillaria in Bacterium lineola. As for Saccharomyces it
undoubtedly contains nuclein, for Raum has prepared it
from yeast cells, and the most recent observer, Macallum,1
is of the opinion that the nuclein is distributed through the
cytoplasm but also aggregated in the so-called granules of
Raum.

The statement therefore can scarcely be called hazardous,
and it is really warranted by the facts at our disposal, for
the more carefully that researches are made, and the more
delicate the methods of investigations employed, the more
is the presence of nuclein demonstrated where it was not
previously supposed to exist.

Macallum's paper, by the way, is of great interest, for he
shows that nuclein is essentially the iron-holding substance
in cells. Knowing as we do the close connection there is
between the presence of iron and the due performance of
the vital processes, this observation opens up a fruitful
source of inquiry as to the dependence of life on chemical
processes.

Throughout this argument I have tried to stick to the
rule of drawing legitimate inferences from observed facts
without wandering into the obscure regions of hypothesis.
If I have been successful and have fairly stated the facts,
and have drawn legitimate inferences, the conclusion which
I come to must be admitted to be of considerable weight.

1 A. B. Macallum, "On the distribution of Assimilated Iron Com-
pounds, other than Haemoglobin and Haematins, in Animal and Vegetable
Cells," Quart. Jour. Mir. Sri., vol. xxxviii., pp. 175-274, 1895.

238 SCIENCE PROGRESS.

The conclusion is this : that life is possible only when two
(or more) substances of complex chemical constitution are
brought together, and that when these two (or more) substances
ai'e brought together we have before us a cell. The cell there-
fore is the vital unit /car' e^o^V. The component parts of
the cell are not vital units, for by themselves they are in-
capable of life; they are the auxiliaries, the indispensable
auxiliaries of life, but they are not themselves living.

This is not a theory of life, and it does not pretend to
be one. It is the generalisation which the facts seem to
warrant, and if it be true, as I believe it must be true, it is
entirely inconsistent with the whole group of theories based
upon hypothetical biophors, gemmules, plasomes, physio-
logical units, plastidules et hoc genus omne. Those theories
are false. And the cell theory is not inadequate, but it is
the only theory which our knowledge of structure and of
life processes permits us to adopt, at least if we confine
ourselves to that part of it which is essential, namely, that
there is one general principle for the formation all tissues,
animal and vegetable, and that principle is the formation of
cells.

Cells are the ultimate vital units, though they are not
the ultimate structural units ; they are the Lebenstrager, or
biophors, and there are no living individuals lower than
cells.

As I have made an effort to stick to facts and have
slighted hypotheses, I shall doubtless incur the profound
contempt of those superior persons who find no mental
repose in things which can be clearly apprehended, but
must leave the material support of earth and seek for rest on
the unsubstantial pillows of cloudland. They will have
abundant scope for exercising their contempt, for my con-
clusion explains nothing, and gives no clue to the problems
of heredity.

As I have said in the earlier part of this essay, I have
no intention to discuss here the complicated problems which
are involved in the question of heredity. I take my stand
on the position from which I started, namely, that if minute

THE PRESENT POSITION OF CELL-THEORY. 239

vital elements occur at all, those same elements which make
life possible and control assimilation and growth must also
be the agents in bringing about the phenomena of heredity.
I have shown that minute vital elements smaller than
cells cannot be believed to exist, and it is clear that the
phenomena of heredity cannot be explained by things
which have no existence. This is a sufficient answer to
those who would say that the phenomena of heredity are
such that we must make use of a hypothesis of minute
vital elements, which are at once the bearers of the vital
qualities and the bearers of the heritable qualities (the his-
toric properties if the expression is preferred) of protoplasm.
It is not true that a theory of heredity is impossible unless
such elements are postulated. Delage has brought forward
a theory of heredity which discards altogether the use of
hypothetical biophors. I pass no criticism on his theory,
favourable or unfavourable, but call attention to it merely
for the purpose of showing that a theory without biophors
is possible. It is no argument to say that the theories
based on ultimate vital units have largely extended our
knowledge of heredity. The Ptolemaic system of astronomy
largely extended men's knowledge of the movements of
the heavenly bodies, but it was not on that account a true
theory.

Moreover, it will be hardly fair to twit me with the
fact that I renounce, for the present, an attempt to explain
the most complicated manifestations of life, for this is only
an essay, and makes no pretence to be the development of
a doctrine.

It is not my present intention to frame hypotheses, not
because I undervalue the use of hypothesis, but because I
regard the first necessary step to be the formation of ideas
appropriate to the facts.

Dr. Whitman has recently written quite a nice little
lecture on the subject of fact and theory, and has directed
it against myself in particular, winding up with a trenchant
paragraph to the effect that the claim to a monopoly of
fact reflects an arrogance which seems to be epidemic.
This homily is fortified by quotations from von Baer,

240 SCIENCE PROGRESS.

Goethe, Huxley and Whewell. Now I never claimed
a monopoly of fact, but that facts should receive a due
share of recognition. Mutual service, as Whitman says,
is the principle which ties theory and fact together ; quite
so, but when theory runs altogether away from fact, the
mutual service is wanting. Fact is a slow servitor, and
drags heavily on the impatient feet of theory. The quota-
tions from Goethe and Huxley do not lend support to the
practice of making hypotheses, rather the contrary. "Ex-
perience. Reflection, Inference " is an excellent motto, but
inference does not mean making hypotheses, nor yet does
the necessary process of generalisation and classification
which Huxley recommends. The passage quoted from the
last-named author condemns the mere cataloguing of facts
under the name of Science, but it does not countenance the
reckless use of theory. As for Whewell's aphorism, let me
commend to Whitman a study of what that author says
with regard to the failure of the Greek schools of philo-
sophy. They did not fail, he says, because they neglected
facts ; the Aristotelian school may be held to have surpassed
the moderns in its appreciation of the value of facts. The
Greeks certainly did not fail for want of boldness in theor-
ising, nor for want of acuteness, of ingenuity and power of
close and distinct reasoning. Nevertheless with all help
from the twin-service of fact and theory their philosophy
was a failure, and why ? Because, as Whewell points out,
their ideas were not distinct and appropriate to the facts.
May not the same thing be said of many of the theories of
cell life and of heredity which have been so much in vogue
in the last few years ? It was my object when I wrote on
Epigenesis and Evolution to show that some ideas then
current, were not appropriate to the facts ; it has been my
object in the present essay to show that certain theories on
cell life, beautifully constructed and ingeniously defended as
they have been, are not appropriate to the facts. I am far from
undervaluing the use of theory, and when I took occasion
before, as I have done again now, to emphasise the impor-
tance of attention to fact, I was not quite so ignorant nor
so arrogant as Whitman supposed. The motto of Goethe

THE PRESENT POSITION OF CELL-THEORY. 241

might well have been reversed for the adornment of the
title pages of some works of the last twenty years. " Theory,
reflection, experience," the last named to be fitted in as best
it might.

Since the above passages were first written the great
work of Yves Delage has came into my hands. Mine is
not the only voice crying out in the great wilderness of
theories. This new voice, however, is far greater and
more powerful than mine. The reader who may be uncon-
vinced by my clumsy argumentation should turn to the
pages of Delage. For clear and candid exposition, trenchant
criticism, and rigorous exposure of defects of reasoning,
they are unsurpassed. Now that this part of my work is
ended I feel that it need never have been begun, for all
that I have had to say has been said in greater detail and
with much greater force by Delage.

FERNS, APOSPOROUS AND APOGAMOUS.

THE normal life cycle of ferns, owing to the micro-
scopic character of their reproductive apparatus,
long baffled the comprehension of botanists. But some
half a century ago, starting with the observations of Naegeli
and Suminski and culminating in those of Hofmeister,
the whole course of their ontogeny has been cleared up.
The fern plant, as ordinarily so-called, produces on the
back of its leaves or fronds, countless numbers of spores,
which are formed within minute capsules or sporangia.
When these spores germinate they give rise, not to a new
fern plant, but to a leaf-like scale — the Prothallus. Upon
the lower surface of this the sexual organs arise, and within
them the sexual cells themselves are differentiated, and as the
result of the fertilisation of one of the female cells or
oospheres, by the male cell or antherozoid, a new fern plant
arises. Thus in normal cases a regular alternation of a
sexual with a sexless generation is seen. But although
this is the course followed by the vast majority of the ferns
which have been hitherto investigated, it is not the only
one open to the plants. Thus Prof. Farlow in 1874 dis-
covered that the formation of the sporophore (fern plant)
generation might arise directly from the oophore (prothallus)
generation, without the intervention of sexual organs, by a
process resembling ordinary budding. De Bary, who
followed the matter further, found that several ferns other
than that examined by Farlow reproduced themselves in
the same fashion, to which phenomenon the name of
Apogamy was given, the marriage link being eliminated.
Curiously enough De Bary found that a variety of one of
our most vigorous British ferns reproduced itself constantly
in this asexual manner, though the common form exhibited
no abnormality in this respect. Recently, however, L.
Kny,1 pursuing these investigations further, has found the

1 Entivickehing von Aspidium Filix mas. Sk'., i Theil., L. Kny,
Berlin.

FERNS, APOSPOROUS AND APOGAMOUS. 243

normal form to reproduce itself in both ways, and since his
asexual examples occurred in thickly-sown pots, it would
appear to be due to some extent to a starved condition
induced by overcrowding, which checks the formation of
the archegonia, and leads to the simple budding in their
place. In all these instances the young plants are en-
gendered upon precisely the same spots on the prothallus
as the sexual one would occupy, and as their development
and appearance are identical, it is only by preliminary
watching that their apogamic origin can be determined.

A case of Apogamy (or rather two cases), however,
recently occurred in a sowing of my own, which is quite
distinct from any I have seen described. A sowing of a
plumose variety of Athyrium jilix foemina failed almost
entirely, only two or three prothalli surviving. One of
these after growing very large, nearly half an inch across,
remained perfectly dormant the whole of the summer ;
early in the autumn, however, the edge of the prothallus
began to grow out and upwards in two places, and eventu-
ally two slightly curved horns,1 each about one quarter
inch long, developed perpendicularly, one on each side of
the indentation or sinus common to most prothalli. Later
on, at a short distance from each tip, a small whitish bulbil
appeared and these increased in size until the circination of
several fronds was plainly visible, a small crown or caudex
being developed. No roots, however, were emitted, and
the two little plants, both, be it remarked, identically
situated and very like in form, were evidently supported by
the prothallic root-hairs, though by this time most of the
prothallus was brown and dead. Subsequently I placed a
piece of loam in contact, and into this both plants rooted
and fronds were sent up, the first of which had no less than
ten pinnate divisions on either side. It was thus, it will be
seen, very different from the usually simple primary fronds
produced either sexually or apogamously heretofore. Later
on still, noticing that the tips of the horns were showing
signs of dilating, I cut these off with a razor and laid them

1 Gard. Chronicle, 10th Nov., 1894.
17

244 SCIENCE PROGRESS.

down, two apparently normal and full-sized prothalli being
the present result. In this case it will be noted that both
plants were far removed from the usual site of reproduction,
and both in this respect and in their vigorous development
are differentiated from previously cited cases of apogamy.
The second case alluded to occurred on another prothallus
in the same pan, wherein the bulbil developed likewise
upon a horn-like excrescence, but on the centre of the upper
surface of the prothallus. This bulbil has developed into
what is so far a very weakly plant of a different type to the
others, but otherwise presenting no special feature.

Until 1884 the Prothallus had always been regarded as
necessarily the offspring of the spore, but in the autumn of
1883 a presumed barren variety of Athyrium jilix fcemina
{var. C/arisstma) was sent me for examination. For
twenty years this plant had been observed to produce an
immense number of apparent sori, but no spores were
ripened or shed, and no offspring had consequently been
raised. Some previous observations on dorsal bulbils, i.e.,
bulbils associated with the spore heaps in this same
species, led me to the opinion that these apparent sori,
which consisted of green pear-shaped masses instead of the
capsules proper to spores, did not represent bulbils, but
some abnormality in the development of the sporangia.
To test this I laid down portions of the fronds, and
to my intense surprise these pearshaped bodies com-
menced at once to grow into prothalli, their tips dilating
and spreading, while root-hairs and subsequently both
archegonia and antheridia appeared in abundance. I at
once gave a note of my observations at the Linnean
Society x as demonstrating the development of the prothallus
without the agency of the spore. The following season,
pursuing my culture, I was able to exhibit a number of
plants and such material as satisfied the society of the
facts put forward.2 Prof. F. O. Bower 3 then undertook

1 " Observations on a Singular Mode of Development in the Lady Fern
{Athyrium filix fosmina)" Linn. Soc. Journal Botany, vol xxi., p. 354-7.

2 " Further notes on ditto,'' ibid., vol. xxi., pp. 358-60.

3 " On Apospory in Ferns (with special reference to Mr. Charles T.
Druery's observations),'' F. O. Bower, ibid., vol. xxi., pp. 360-68.

FERNS, APOSPOROUS AND APOGAMOUS. 245

the further investigation of the case, and found that the
development of the sorus or spore heap went as far as the
formation of the stalk of the sporangium or spore capsule,
but at that stage it stopped and a vegetative growth set in
to form the clusters of pear or club-shaped bodies which
eventually went through the normal evolution of prothalli
and sexual plants. Mr. G. B. Wollaston followed by
providing material from a variety of Polystichum angulare
in his possession, wherein the elimination of the spore and
the entire soral apparatus was so complete that the prothalli
were developed from the slender-pointed tips of the ultimate
divisions of the fern-frond. Padley, P. ang. var pule her rinmm
was the plant in question, and as it chanced that several
other varieties of the same type existed, though found at
widely sundered spots in England, it resulted that Dr.
F. W. Stansfield and myself found the same character in
two of them. Prof. Bower further observed that soral
apospory, i.e., the form first noted, was also present on
Padley's plants, and this too we, Dr. Stansfield and my-
self, confirmed in the others. We have in these four
examples, and in the genus Polystichum especially, ample
proof that the spore is not an essential preliminary to
the existence of the Prothallus, but that the latter may
be developed direct from the tissues of the Sporophore,
precisely as this latter in Apogamy may be developed
direct from those of the oophore.1 Curiously enough
the next case which came before the writer's notice
was an aposporous seedling of the same variety of Lastrea
(Aspidium) determined by De Bary as being persistently
apogamous, viz., Lastrea pseudo ?nas var. cristata. This
case was distinct from previous ones as it was a young
plant and not an adult, which produced the prothalli. The
tip of the second frond evolved from the prothallus (the
first was eaten off and was not seen) bore a prothallus of
the normal form. Subsequently this and the succeeding

1 Professor F. O. Bower subsequently prepared an exhaustive mono-
graph "On Apospory and Allied Phenomena". Linnean Transactions,
vol. ii., part 14, July, 1887, to which reference should be made for details
of the preceding cases.

246 SCIENCE PROGRESS.

frond became covered with prothalli developed not merely
from the edges, but also from the upper surface, and being-
pegged down produced a number of plants, but whether
apogamously or not I cannot say, though from De Bary's
observations, they should be so. It is worthy of remark
that in some of these youngsters, the line between the two
generations of sporophore and oophore was so vague that
the primary fronds were simply stalked prothalli, the next
frond half one and half the other, while the fourth or
fifth had quite outgrown the tendency and were of the
typical varietal form. This plant was exhibited and de-
scribed at the Linnean Society, 3rd November, 1892.1 Of
the next two cases I observed, the first was an Athyrium
found in Lancashire and exhibited in 1893 at the meeting
of the Pteridological Society at Lancaster by Mr. Bolton
the finder. Immediately on seeing it I remarked, "How
very like Col. Jones's Clarissima," simultaneously with which
Mr. Bolton said, " It is strange, but it never ripens its
spores " ". Turning the frond over, the reason was clear,
it was perfectly white with aposporal excrescences. On
submitting these to culture they produce plants freely by
sexual action, but of two types, one very depauperate, mere
skeleton plants, and the other of the parental form with
occasional reversion towards the normal. In some of these
young plants the whitish excrescences are plentiful in
fronds only an inch or two high, and there are evident
signs of prothalloid growth at the tips of the segments as
well, pointing to apical apospory when the plants are more
developed. The next case occurs in a most unlikely species,
especially as apical apospory is in question. This is seen
in a variety of Scolopendrium vulgare (S. v. cri spurn
DrummondicB) which occurs in the wild state, like all the rest,
characterised by being frilled and crested, and having more-
over a finely fimbriated edge to the fronds. Visiting Mr.
Bolton to inspect the Athyrium last cited, I saw a fine plant of
this fern, and it immediately struck me that the tips of

lu Notes on an Aposporous Lastrea (Nephrodium)" Linn. Soc. Journal
Botany, vol. xxix., pp. 479-82.

FERNS, APOSPOROUS AND APOGAMOUS. 247

the fimbriate projections were remarkably translucent. I
obtained material, laid it down, and at once prothalli began
to develop vigorously from every point, so vigorously
indeed that a single tip has formed a mass of prothalli an
inch across which yielded at least a dozen plants of the
parental form.1

Dr. F. W. Stansfield has recently sent me prothalli
developed from a finely fimbriated form of Lastrea of
which the reputed parent is that already described, and in-
forms me that it is profusely aposporous though fairly de-
veloped in size.

By the various instances of this phenomenon so far
cited, we see that the normal life cycles of the ferns in
question have been successively shortened, first by the
elision of the spore and then by that of the whole soral
apparatus, while if we accept De Bary's observations as
establishing the constant apogamous reproduction of L.
pseudo mas cristata, in that case, it is shortened almost to
the utmost, the chain being simply sporophore, prothallus,
sporophore. Consistently indeed with the alternation of
generation the chain could not apparently be shorter since
the prothallus being eliminated we naturally come, or
seem to come, to simple bulbils, such as occur on many
ferns, Aspleniuvi bulbiferum for example. In the final
case, however, which I have to cite, we arrive at the
elimination even of the prothallus by substitution of the
frond itself as the oophore or egg-bearer, the archegonia
and antheridia being generated upon the frond without the
prior formation of a prothallus proper. In a small plant
of Scolopendrium vulgare recently sent me by Mr. E. J.
Lowe, and exhibited by me at the Linnean Society in
November last, although a definite axis of growth had been
formed and several fronds had arisen in the normal spiral
fashion around it, indicating that the prothallus stage had
been unmistakeably passed, each of these fronds bore a
thickened cushion at its tip upon which were seated both

1<lNote on Apospory in a form of Scolopendrium vulgare" etc., Linn.
Soc. Journal, vol. xxx., pp. 281-84.

248 SCIENCE PROGRESS.

antheridia and archegonia, accompanied by aerial roothairs,
the frond itself thus assuming the functions of the pro-
thallus. Mr. Lowe raised a number of similar plants on
the genesis of which he is preparing a paper which I will
not forestall ; but he informs me that in time they throw
off this aposporous character. Fronds which he has sent
me, and which I have laid down, have developed prothalli
all over their surface and at all terminals, but so far my
cultures are too recent to permit me to report the advent of
plants.

This completes the sketch of the cases which have
come under my immediate notice, but considering that, in-
cluding the first discovery, the phenomenon has been
observed in no less than nine instances in our limited num-
ber of British species, viz., Lastrea [Nephrodium) two, Athy-
rium filix fcemina two, Polys tic hum angular e three, and
Scolopendrium vulgare two ; it is only reasonable to ex-
pect that many undiscovered instances must occur in the
innumerable other species existent throughout the world.

Charles T. Druery.

Science progress*

No. 28.

June, 1896.

Vol. V.

THE GROWTH OF OUR KNOWLEDGE OF

HELIUM.

THE DISCOVERY OF THE LINE D3, 1868.

IN the year 1868, spectrum analysis was first utilised in
endeavouring" to unravel the message which was con-
veyed to us by a most interesting eclipse observed in India.
The diagrams will indicate the kind of record with which
we have to deal in studying these celestial hieroglyphics.
We are in one part dealing with the long waves of light,
the red ; we are in the other dealing with the shorter waves
of light, the blue. The work done in that eclipse is
indicated by the bright lines — the hieroglyphics — which,
when translated as they have been, describe for us the
chemical nature of the particular stuff in the sun, which
made him put on a blood-red appearance " on his getting
out of his eclipse ". Taking the notes in the light scale
which are lettered in the ordinary spectrum of sunlight, in
order that they may be easily recognised and remembered,
we learn the particular qualities of the light emitted by the
blood-red streak.

We have one quality represented by the line D, another
at C, and another at F. According to the diagram, one of
the lines is in the position of D. One observer said it was
"at D, or near D ".

Soon after this eclipse was observed in India, a method,

18

250

SCIENCE PROGRESS.

long before formulated, of studying the blood-red streak
surrounding the sun without waiting for an eclipse was
brought into operation.

By this method it was quite easy to make observations
whenever the sun was shining, perfectly free from any of
the difficulties attending the hurry and the worry and the
excitement of an eclipse, which lasts only a few seconds.

B C -D Ef F G

Fig. i. — Pogson's diagram of the spectra of the sun's surroundings in the
Eclipse of 1868. The bright lines seen are shown in the upper part
of the diagram ; the chief lines in the solar spectrum, red to the left,
blue to the right, are shown in the lower part.

A 1

BC

D Eb

F G

H

J

. 1

Ha

H/» Hr

BB

■

I

Fig. 2. — Summation of the observations of the spectrum of the
sun's surroundings in the Eclipse of 1868. (1) Solar
spectrum showing the position of the chief lines. (2)
Rayet's observations of bright lines. (3) Herschel's obser-
vations of bright lines. (4) Tennant's.

Further, as the method consists of throwing an image of
the sun, formed by a telescope, on to the slit of a spectro-
scope, so that the spectrum of the sun's edge and of the
sun's surroundings can be seen at the same time, exact
coincidence or want of coincidence between the bright and
dark lines can be at once determined. During an eclipse

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 251

this of course is not possible, as the ordinary spectrum of
the sun, with its tell-tale dark lines, is invisible because the
sun, as we ordinarily see it, is hidden by the moon.

Working, then, under such very favourable conditions, it
was seen that there was certainly a red line given by this lower

1

I

Fig. 3. — The exact coincidence of the red line with the dark line C.

part of the solar atmosphere coincident with the very im-
portant line in the solar spectrum which we call C.

Another part of the spectrum in the blue-green was
examined, and there again it was seen that the parts out-
side the sun gave us a bright line exactly in the position of

> ii 1 1 1 11 1 1 1 1 1 1 I ■

Fig. 4. — The exact coincidence of the blue-green line with the dark line F.

the obvious dark line in the solar spectrum which is called
F ; so that with regard to those two most important lines,
there was no doubt whatever that we were dealing with
the substance which produces these dark lines in the solar
spectrum.

252

SCIENCE PROGRESS.

Fig. 5 is a diagram of the yellow, or rather the orange,
part of the solar spectrum, showing two very important
lines, which are called the lines D, due to the metal sodium,
the investigation of which was just as important in solving
the celestial hieroglyphics we call spectral lines as the
Rosetta stone was important in settling the question of the
Egyptian ones.

Pogson, in referring to the eclipse of 1868, said that the
orange line was "at D, or near D ". We see from the

D1 D2

Fig. 5. — The want of coincidence of the orange line D3 with the dark

lines D1 and D2.

diagram (Fig. 5) that the new method indicated that "near
D " was the true definition. The line in this position in
the spectrum, unlike the other two lines which I have
indicated, has no connection at all with any of the dark
lines in the ordinary solar spectrum. We were therefore
perfectly justified in attaching considerable importance to
this divergence in the behaviour of this line, taking the
normal behaviour to be represented by the two strong lines
in the red and the blue-green. The new line was called
D3 to distinguish it from the sodium lines D1 and D2.

A considerable amount of work was done with regard
to the orange line. It was found that there was no sub-
stance in our laboratories which could produce it for us,
whereas in the case of the line D we simply had to burn
some sodium, or even common salt, in a flame to produce
it, and the other lines in the red and the blue-green were
easily made manifest by just enclosing hydrogen in a
vacuum tube, and passing an electric current through it,

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 253

or observing the spectrum of a spark in a stream of coal-
gas.

Now at the first blush it looked very much as if this
line was really due to the same element which produced
the others at C and F, and it was imagined that the reason
we did not see it in our laboratories was because it was a
line which required a very considerable thickness of hydro-
gen to render it visible. That was the first idea, and Dr.
Frankland and myself found that there was very consider-
able justification for this view, because a simple calculation
showed that the thickness of the solar atmosphere, which
was producing that orange line under the conditions which
enabled us to see it in our instruments by looking along the
edge of the sun, was something like 200,000 miles.

ABC
Fig. 6. — Changes of wave-length of the F hydrogen line when a solar
cyclone is observed. A, the change towards the red indicates the
retreating side of cyclone. C, the change towards the blue indicates
the advancing side. B, the whole cyclone is included in the width of
the slit, and both changes of wave-length are visible.

Hence, in order to get a final decision on this point,
there was nothing for it but to tackle the question from a
perfectly different point of view, and the different point of
view was this. The work had not gone on very long
before one found minute alterations in the positions of these
lines in the spectrum ; the orange line, for instance, might
sometimes be slightly on one side, and sometimes on the
other of its normal position. Further work showed that in
these so-called " changes of wave-length " we had a precious
means of determining the rate of movement of the gases
and vapours in the solar atmosphere.

Fig. 6 indicates how these changes of wave-lengths are

254 SCIENCE PROGRESS.

shown in the spectroscope. The lines are contorted in both
directions, and sometimes to a very considerable extent,
indicating wind movements on the sun, reaching and some-
times exceeding ioo miles a second.

We had here a means of determining whether the
orange line was produced by the same gases which gave the
red and blue lines, because if so, when we got any altera-
tion in the position of the red and blue lines, which always
worked together, we should get an equivalent alteration in
the position of the orange one.

I found that the orange line behaved quite differently
from either the red or the blue lines ; so then we knew that
we were not dealing with hydrogen ; hence we had to do
with an element which we could not get in our laboratories,
and therefore I took upon myself the responsibility of coin-
ing the word helium, in the first instance for laboratory
use.

This kind of work went on for a considerable time, and
what one found was, that very often in solar disturbances
we certainly were dealing with some of the lines of sub-
stances with which we are familiar on this earth ; but at the
same time it was very remarkable that when the records
came to be examined, as they ultimately were with infinite
care and skill, it was found that not only did we get this
line in the orange indicating an unknown element associated
with substances very well known, like magnesium, but that
there were many other unknown lines as well. Within a
few months of my first observations, several new lines about
which nothing was known were thus observed.

THE DISCOVERY OF OTHER UNKNOWN LINES, 1869.

The place of the orange line D3 I determined on
20th October, 1868. Among many other lines behaving
like it, two at wave-lengths 4923 and 5017 were discovered
in June, 1869, and afterwards another at 6677, while Pro-
fessor Young noted another in September, 1869, at 4471.
He wrote : —

" I desire to call special attention to 2581*5 [ = 4471 on

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 255

Kirchhoff's scale], the only one of my list, by the way,
which is not given on Mr. Lockyer's. This line, which was
conspicuous at the Eclipse of 1869, seems to be always
present in the spectrum of the chromosphere. . . . It has no
corresponding dark line in the ordinary solar spectrum, and
not improbably may be due to the same substance that
produces D3."

This same line was noted also by Lorenzoni and named
f. Another line at 4026 was added later by Professor
Young.

Fig. 7. — Tacchini's observations of two slight solar disturbances
showing the height to which the layers of the different gases
extend. Magnesium vapour is highest of all, and is furthest
extended ; next comes a gas of still unknown origin, indicated
by a line at 1474 of Kirchhoff's scale and so on.

Then with regard to solar disturbances. Let me refer
in detail to a diagram indicating some results arrived at by
the Italian observers. We are dealing with the spectro-
scopic record of two slight disturbances in a particular part
of the sun's atmosphere. The spectroscope tells us that in
that region there was a quantity of the vapour of magnesium
which is collected in that place. Then we find that another
substance, about which we again know nothing whatever,
is also visible in that region, and then we get the further
fact that in those particular disturbances we get four other
spectral lines indicated as being disturbed, and of those four
lines we only know about one.

256 SCIENCE PROGRESS.

In that way it very soon became perfectly clear to those
who were working at the sun, that in all these disturbances,
or at all events in most of them, we were dealing to a large
extent with lines not seen in our laboratories when dealing
with terrestrial substances ; this work went on till ultimately,
thanks to the labours of Professor Young in America, we
had a considerable list of lines coming from known and un-
known substances which had been observed under these
conditions in solar disturbances, and Professor Young was
enabled to indicate the relative number of times these lines
were visible. For instance, the lines which are most
frequently seen under these conditions he tabulated as
represented by the number 100, and of course the line
which was least frequently seen would be represented by
1 ; and therefore from these so-called "frequencies" we
got a good idea of the number of times we might expect
to see any of these disturbance-lines when anything was
going on in the sun.

It was this kind of work which made Tennyson write
those very beautiful lines :

" Science reaches forth her arms
To feel from world to world ".1

1 And then he added :

" and charms
Her secret from the latest moon ".

I mention this because Tennyson, whose mind was saturated with
astronomy, had already grasped the fact that what had already been done
was a small matter compared with what the spectroscope could do ; and
now the prophecy is already fulfilled, for by means of the spectroscopic
examination of the light from the stars we can tell that some of them are
double stars, that is to say, in poetic language, stars with attendant moons.
Although we can thus charm the secret from each moon by means of the
spectroscope, to see the moon it would require (in the case of (3 Aurigse) a
telescope not eighty feet long, but with an object-glass eighty feet in dia-
meter, because the closer two stars are together the greater must be the
diameter of the object-glass, independently cf its focal-length and magnifying
power.

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 257

DR. HILLEBRAND'S RESEARCHES ON URANINITE, 1888.

In this year Dr. Hillebrand, one of the officials in the
Geological Department at Washington, was engaged upon
the chemical examination of specimens of the mineral
uraninite from various localities.

He dealt with crystals which he put in a vessel contain-
ing some sulphuric acid and water. He found that bubbles
of gas were produced out of the crystal by means of the
sulphuric acid. He collected this gas and came to the
conclusion that it was nitrogen.

This result was new. He thus wrote about it : —

"In consequence of a certain observation " [the one I
have just referred to] " and its results, an entirely new
direction was given to the work, and its scope wonderfully
broadened. This was the discovery of a hitherto un-
suspected element in uraninite, existing in a form of com-
bination not before observed in the mineral world."

It is not needful here to follow -Dr. Hillebrand through
all the painstaking and patient labour he cut out for him-
self to explain this anomalous behaviour. Needless to
say he did not omit to employ the spectroscope to test the
nature of the new gas.

His observations were thus described : — 1

"In a Geissler tube under a pressure of ten milli-
metres and less, the gas afforded the fluted spectrum of
pure nitrogen as brilliantly and as completely as was done
by a purchased nitrogen tube. In order that no possibility
of error might exist, the tube was then reopened and
repeatedly filled with hydrogen, and evacuated till only the
hydrogen lines were visible. When now filled with the
gas and again evacuated, the nitrogen spectrum appeared
as brilliantly as before, with the three bright hydrogen lines
added."

On this paragraph I may remark that it has long been
known that gases like nitrogen give us quite distinct spectra
at different temperatures — one fluted, another containing

1<(On the Occurrence of Nitrogen in Uraninite," Bulletin, No. 78,
U.S. Geol. Survey, 1889-90, p. 55.

258 SCIENCE PROGRESS.

lines. Which of these we shall see in a tube will depend
upon the pressure of the gas and the electric current used.
The fluted spectrum of nitrogen is very bright and full of
beautiful detail in the orange part of the spectrum ; the line
spectrum, on the other hand, is almost bare in that region.

It is important to note that it so happened 'that the pressure
and electric conditions employed by Dr. Hillebrand enabled
him generally to see the fluted spectrum. This however
was not always the case. In an interesting letter to Pro-
fessor Ramsay he writes (Proc. Roy. Soc, vol. lviii., p. 81): —

" Both Dr. Hallock and I observed numerous bright
lines on one or two occasions, some of which apparently
could be accounted for by known elements — as mercury, or
sulphur from sulphuric acid ; but there were others which I
could not identify with any mapped lines. The well-known
variability in the spectra of some substances under varying
conditions of current and degree of evacuation of the tube
led me to ascribe similar causes for these anomalous appear-
ances, and to reject the suggestion made by one of us in a
doubtfully serious spirit, that a new element might be in
question."

Dr. Hillebrand concludes his paper as follows : —

"The interest in the matter is not confined merely to a
solution of the composition of this one mineral ; it is broader
than that, and the question arises : May not nitrogen be a
constituent of other species in a form hitherto unsuspected
and unrecognisable by our ordinary chemical manipulations?
And, if so, other problems are suggested which it is not now
in order to discuss."

D3 AND OTHER UNKNOWN LINES IN NEBULA, 1890.

A negative of the nebula of Orion, taken at my observatory
at Westgate-on-Sea in 1890, contains fifty-six lines, and of
course by determining, as we have been able to do approxi-
mately, the wave-lengths — the positions of these lines in
the spectrum — we can determine the exact light notes
represented, and therefore the substances which produce
them. In this spectrum of the nebula of the Orion were

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 259

lines of unknown origin exactly coinciding with those un-
known lines which I have already referred to as having
been seen in the sun's atmosphere. Some of the un-
known lines in that atmosphere, those that we have not
been able to see in our laboratories, are identical in position
with some of the unknown lines in the nebula of Orion.

I may remark that as early as 1886 Dr. Copeland had
discovered D3 in the visible spectrum of the nebula, and
in a letter to him I had suggested that another line he had
recorded at 447 might be Lorenzoni's f\ this he thought
to be probable. The matter was set for ever at rest by
the photograph which established the presence of 4471 and
4026 as well, already noted as a solar line.

Professor Campbell, of the Lick Observatory, obtained
other photographs of the spectrum of the nebula some two
or three years after mine was taken. In the following list
of lines in my photograph an asterisk denotes that Campbell
gives a line nearly in the same position. He recorded
no line which did not appear on my photograph.

3896*
3888*
401 1
4026*
4121*

4143*

4168

4390*

4472*

4716*

4924

5875-8 = D3
THE SAME UNKNOWN LINES OCCUR IN THE STARS, 1892.

About the year 1890 I began the photography of stellar
spectra at Kensington, with special reference to their
classification on the basis of the chemical constituents
established by their spectra. By 1892 several important
results had been obtained, while the progress of this branch
of science lately has been so considerable that any state-
ment regarding the positions of lines, and therefore the

260 SCIENCE PROGRESS.

chemical origins of them, may be made with a considerable
amount of certainty as depending upon very accurate work.

The various classes in which the stars have been
classified by different observers according to their spectra
are discussed elsewhere, but some of the more salient differ-
ences must be pointed out here ; thus we have stars with
many lines in their spectra, others with comparatively few.
I will take the many-lined stars first.

The diagram (Fig. 8) represents the spectrum of
Arcturus, a star the spectrum of which closely resembles
that of the sun. In a Cygni we have another star with
many lines, but here we note, when we leave the hydrogen
on one side and deal with the other stronger lines, that
there is little relation between the solar spectrum and these
lines.

I next come to the stars with few lines : these are well
represented by many of the chief stars in the Constellation
of Orion. Bellatrix is given as an example (Fig. 9).

Then, I have next to say that in the photographs of the
spectra of many stars, chiefly of those more or less like
Bellatrix, we found the same lines which we have so far
classified as unknown for the reason that in our laboratories
we have not been able to get any lines which correspond
with them. I again mention D3, 4471 and 4026, previously
noted as appearing both in the chromosphere and in the
nebula of Orion.

But the thing is much more interesting even than this ;
not only these, but all the chief unknown lines appearing in
the nebula of Orion are also found in these stars. And this
is so absolutely true that there is no necessity to give a list
of the unknown lines seen in Bellatrix ; every one of them
given in the nebula has found its place, and (so far) practically
no others.

This of course marked a great development of the
inquiry, and makes the question of the unknown lines
more important than ever.

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 261

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262 SCIENCE PROGRESS.

PHOTOGRAPHIC RESULTS DURING A SOLAR ECLIPSE, 1893.

A method which was first employed by Respighi and
myself during the eclipse of 1871, was employed on a
large scale and with great effect during the eclipse of 1893.
The light proceeding from the luminous ring round the
dark moon was made to give us a series of rings, represent-
ing each bright line seen by the ordinary method on a
photographic plate. The observers this time were stationed
in West Africa and in Brazil. The African station was
up one of the rivers, not very far away from the town of
Bathurst. The Brazilian station was near Para Curu. The
same instrument which was previously referred to as used for
obtaining photographs of the stars was sent to the African
station in order that photographs of the eclipse of the sun
might be taken on exactly the same scale as the photo-
graphs of the stars had been, so that the stellar and solar
records in the photographs might be compared. The results
obtained by Messrs. Fowler and Shackleton, who were in
charge of the instruments at the two stations, will be gathered
from the accompanying diagrams, Figs. 10 and 11.

We get more or less complete rings when we are deal-
ing with an extended arc of the chromosphere, or lines of
dots when any small part of it is being subjected to a dis-
turbance which increases the temperature and, possibly,
the numbers of the different vapours present.

The efficiency of this method of work with the dis-
persion employed turns out to be simply marvellous, and in
securing such valuable and permanent records as these, we
have done very much better than if we had contented our-
selves with the style of observations that I have referred to
as having been made in 1871.

As was expected the comparison between solar and
stellar records thus rendered possible enabled a very great
advance to be made.

On examining these eclipse records, we find that we
have to do exactly with those unknown lines which had
already been photographed in the stars and in the nebulas.

As was to be expected we, of course, deal with the lines

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 263

264 SCIENCE PROGRESS.

recorded in the first observations of the solar disturbances,
and chronicled in that table of Professor Young's to which
I have already called attention ; but the important thing is
the marvellously close connection between eclipse- and star-
spectrum photographs so far as the "unknown lines" are
concerned.

Nearly all the lines given in the table on p. 259 as
visible in the Nebula of Orion and afterwards found in
Bellatrix, are also among the lines photographed during the
eclipse.

DISCOVERY OF A TERRESTRIAL SOURCE OF HELIUM, 1895.

The year 1894 was made memorable by the announce-
ment of the discovery by Lord Rayleigh and Professor
Ramsay of a new gas called argon, and you know that the
discovery was brought about chiefly in the first instance
by the very accurate observations of Lord Rayleigh, who
found that when he was determining the weight of air in
the globe of a certain capacity, the weight depended upon
the source from which he got the nitrogen.

From the nitrogen from atmospheric air he obtained one
weight, and from that obtained by certain chemical pro-
cesses he obtained another, and ultimately it was found that
there was an unknown element which produced these results,
these various changes in the weight, and as a consequence
we had the 1895 discovery of argon.

Early in 1895 it struck Mr. Miers, of the British
Museum, that it might be desirable to draw attention to
the nitrogen which we have seen Dr. Hillebrand in 1888
obtaining from his crystal of uraninite ; his observations, of
course, were more in the mind of Mr. Miers than in the
minds of the pure chemists. He therefore communicated
with Professor Ramsay, who lost no time, because it was
very interesting to study every possible source of nitrogen
and see what its behaviour was in regard to the quantity
of argon that it produced, and in the relation generally of the
gas to the argon which was produced from it.

Professor Ramsay treated uraninite in exactly the same

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 265

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266 SCIENCE PROGRESS.

way that Dr. Hillebrand had done in 1888. The gas
obtained as Dr. Hillebrand had obtained it was eventually-
submitted to a spectroscopic test, following Dr. Hillebrand's
example. But here a noteworthy thing comes in.

It so happened that the pressure and electrical conditions
employed by Professor Ramsay were so different from those
used by Dr. Hillebrand that, although nitrogen was un-
doubtedly present, the fluted spectrum which, as I have
previously stated, floods the orange part of the spectrum
with luminous details, was absent. But still there was
something there.

Judge of Professor Ramsay's surprise when he found
that he got a bright orange line ; that was the chief thing,
and not the strong suggestion of the spectrum of nitrogen.
Careful measurements indicated that the twenty-six-year-
old helium had at last been run to earth, D3 was at last
visible in a laboratory. Professor Ramsay was good enough
to send specimens of the tubes containing this gas round
to other people, and he sent one of them to me.

I received Professor Ramsay's tube on 28th March, but
it was not suitable for the experiments I wished to make.

On 29th March, therefore, as Professor Ramsay was
absent from England, in order not to lose time I determined
to see whether the gas which had been obtained by chemical
processes would not come over by heating in vacuo, after the
manner described by me to the Royal Society in 1879/and Mr.
L. Fletcher was kind enough to give me some particles of
uraninite (broggerite) to enable me to make the experiment.

This I did on 30th March, and it succeeded ; the gas
giving the yellow line came over, associated with hydrogen,
in good quantity.

From 30th March onwards my assistants and myself
had a very exciting time. One by one the unknown lines
I had observed in the sun in 1868 were found to belong to
the gas I was distilling from broggerite ; not only D3 but
4923, 5017, 4471 (Lorenzoni's/), 6677 (the B C of Fig. 7),
referred to previously, and many other solar lines, were all
caught in a few weeks.

1 Roy. Soc. Proc, vol. xxix., p. 266.

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 267

But this was by no means all. The solar observations
had been made by eye, and referred therefore to the less
refrangible part of the spectrum, but I had obtained and
studied hundreds of stellar photographs, so I at once pro-
ceeded to photograph the gas and compare its more re-
frangible lines with stellar lines.

Here, if possible, the result was still more marvellous.
In the few-lined stars by 6th May I had caught nearly all
the most important lines at the first casts of the spectroscopic
net. Fig. 1 5, which includes some later results, will give an
idea of the tremendous revelation which had been made as
to the chemistry of some of the stages of star-life. I
pointed out on 8th May that we had already "run home "
the most important lines in the spectra of Group III. in
which stars alone we find D3 reversed.

These results enabled us at once to understand how it
was that the "unknown lines" had been seen both in the
sun's chromosphere and some nebulae and stars. The gas
obtained from the minerals made its appearance in the
various heavenly bodies in which the conditions of the
highest temperatures were present ; and the more the work
goes on, we find that this gas is really the origin of most,
but certainly not of all, of the unknown lines which have
been teasing astronomical workers for the last quarter of a
century.

THE FIRST INVESTIGATIONS OF THE SPECTRUM OF THE

GAS FROM CLEVEITE.

The dates of the papers communicated to the Royal
Society recording the observations of the lines in the gas
obtained from minerals which had been previously recorded
are as follows : —

4026

4922

The lines at 667 and 5016 had been previously seen
by Thalen (Comptes Rendus, 16th April, 1895).

25 th April, -

- 447i

4144

8th May,

- 667

4388

9th May,

- 3889

28th May, -

- 7065

29th May, -

- 5048

5016

268 SCIENCE PROGRESS.

Although the general distribution and intensities of the
lines in the gases from broggerite and cleveite sufficiently
corresponded with some of the chief " unknown lines " in
the solar chromosphere and some of the stars to render
identity probable, it was necessary to see how far the con-
clusion was sustained by detailed investigations of the
wave-lengths of the various lines.

EMPLOYMENT OF HIGH DISPERSION.

This was practically a separate branch of the work, as
the observations had to be made in the observatory. Next
I give here the observations relating- to D3, 4471.

The Orange Line, A 5875*9. — Immediately on receiving
from Professor Ramsay, on 28th March, a small bulb of the
gas obtained from cleveite, a provisional determination of
wave-length was made by Mr. Fowler and myself, in the
absence of the sun, by micrometric comparisons with the D
lines of sodium, the resulting wave-length being 5876*07
on Rowland's scale. It was at once apparent, therefore,
that the gas line was not far removed from the chromo-
spheric D3, the wave-length of which is given by Rowland

as 5875'98.

The bulb being too much blackened by sparking to give
sufficient luminosity for further measurements, I set about
preparing some of the gas for myself by heating broggerite
in vacuo, in the manner I have already described. A new
measurement was thus secured on 30th March, with a
spectroscope having a dense Jena glass prism of 6o° ; this
gave the wave-length 5876*0.

On 5th April, I attempted to make a direct comparison
with the chromospheric line, but though the lines were
shown to be excessively near to each other, the observa-
tions were not regarded as final.

Professor Ramsay having been kind enough to furnish
me, on 1st May, with a vacuum tube which showed the
orange line very brilliantly, a further comparison with the
chromosphere was made on 4th May. The observations
were made by Mr. Fowler, in the third order spectrum of
a grating having 14,438 lines to the inch, and the observing

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 269

telescope was fitted with a high power micrometer eye-
piece ; the dispersion was sufficient to easily show the
difference of position of the D3 line on the east and west
limbs, due to the sun's rotation. Observations of the
chromosphere were therefore confined to the poles.

During the short time that the tube retained its great
brilliancy, a faint line, a little less refrangible than the
bright orange one, and making a close double with it, was
readily seen ; but afterwards a sudden change took place,
and the lines almost faded away. While the gas line was
brilliant, it was found to be " the least trace more refrangible
than D3, about the thickness of the line itself, which was
but narrow" ("Observatory Note Book"). The sudden
diminution in the brightness of the lines made subsequent
observations less certain, but the instrumental conditions
being slightly varied, it was thought that the gas line was
probably less refrangible than the D3 line by about the
same amount that the first observation showed it to be
more refrangible. Giving the observations equal weight,
the gas line would thus appear to be probably coincident
with the middle of the chromospheric line, but if extra
weight be given to the first observation, made under much
more favourable conditions, the gas line would be slightly
more refrangible than the middle of the chromosphere line.

Pressure of other work did not permit the continuation
of the comparisons. In the meantime, Runge and Paschen
announced (Nature, vol. Hi., p. 128) that they also had seen
the orange line of the cleveite gas to be a close double,
neither component having exactly the same wave-length as
D3, according to Rowland.

They give the wave-length of the brightest component as
5878*883, and the distance apart of the lines as 0*323.

This independent confirmation of the duplicity of the
gas line led me to carefully re-observe the D3 line in the
chromosphere for evidences of doubling. On 14th June
observations were made by Mr. Shackleton and myself of
the D3 line in the third and fourth order spectra under
favourable conditions ; " the line was seen best in the fourth
order, on an extension of the chromosphere or prominence

270 SCIENCE PROGRESS.

on the north-east limb of the sun. The D3 line was seen
very well, having every appearance of being double, with a
faint component on the red side, dimming away gradually ;
the line of demarcation between the components was not
well marked, but it was seen better in the prominence than
anywhere else on the limb " (" Observatory Note Book ").

It became clear, then, that the middle of the chromo-
sphere line, as ordinarily seen, and as taken in the
comparison of 4th May, does not represent the place of
the brightest component of the double line, so that exact
coincidence was not to be expected.

The circumstance that the line is double in both gas
and chromosphere spectrum, in each the less refrangible
component being the fainter, taken in conjunction with the
direct comparisons which have been made, rendered it
highly probable that one of the gases obtained from cleveite
is identical with that which produces the D3 line in the
spectrum of the chromosphere.

Other observers have since succeeded in resolving the
chromospheric line. On 20th June, Professor Hale found
the line to be clearly double in the spectrum of a promin-
ence, the less refrangible component being the fainter, and
the distance apart of the lines being measured as 0*357
tenth -metres (Ast. JVac/i., 3302).

The doubling was noted with much less distinctness in
the spectrum of the chromosphere itself on 24th June.
Professor Hale points out that Rowland's value of the wave-
length (as well as that of 5875*924, determined by himself
on 19th and 20th June) does not take account of the fact
that the line is a close double.

Dr. Huggins, after some failures, observed the D3 line
to be double on 10th July [Ast. Nack., 3302); he also
notes that the less refrangible component was the fainter,
and that the distance apart of the lines was about the same
as that of the lines in the gas from cleveite, according to
Runge and Paschen.

It may be added, that in addition to appearing in the
chromosphere, the D3 line has been observed as a bright
line in nebulae by Dr. Copeland, Professor Keeler and

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 271

others ; in /3 Lyrae and other bright line stars ; and as a
dark line in such stars as Bellatrix, by Mr. Fowler, Pro-
fessor Campbell and Professor Keeler. In all these cases
it is associated with other lines, which, as I shall show pre-
sently, are associated with it in the spectra of the new gases.

The Blue Line, A 4471*8. — A provisional determination
on 2nd April of the wave-length of a bright blue line, seen
in the spectrum of the gases obtained from a specimen of
cleveite, showed that it approximated very closely to a
chromospheric line, the frequency of which is stated as 100
by Young.

This line was also seen very brilliantly in the tube
supplied to me by Professor Ramsay on 1st May, and on
6th May it was compared directly with the chromosphere
line by Mr. Fowler. The second order grating spectrum
was employed. The observations in this region were not
so easy as in the case of D3, but with the dispersion em-
ployed, the gas line was found to be coincident with the
chromospheric one. In this case also, the chromosphere
was observed at the sun's poles, in order to eliminate the
effects due to the sun's rotation.

Besides appearing in the spectrum of the chromosphere,
the line in question is one of the first importance in the
spectra of nebulae, bright line stars, and of the white stars
such as Bellatrix and Rigel.

The Infra-red Line, \ 7065*5. — In addition to D3 and
the line at 447 1 '8, there is a chromospheric line in the infra-
red which also has a frequency of 100, according to Young.
On 28th May I communicated a note to the Royal Society
stating that this line had been observed in the spectrum of
the gases obtained from broggerite and euxenite {Roy. Soc.
Proc, vol. lviii., p. 192), solar comparisons having con-
vinced me that the wave-length of the gas line corresponded
with that given by Young ; and I added : " It follows, there-
fore, that besides the hydrogen lines all three chromospheric
lines in Young's list which have a frequency of 100 have
now been recorded in the spectra of the new gas or gases
obtained from minerals by the distillation method ".

M. Deslandres, of the Paris Observatory, has also

272 SCIENCE PROGRESS.

observed the line at 7065 in the gas obtained from the
cleveite (Comptes Rendus, 17th June, 1895, p. 1 331).

A great deal of work has been done upon these gases
from other points of view than those which affect their
cosmical relations, and perhaps I may be allowed next to
refer to some of the results which have been obtained by
myself.

HELIUM NOT CONNECTED WITH ARGON.

The first point is that the gas from the minerals contains
no argon. Dr. Ramsay in his first experiments came to the
conclusion that the spectra of argon and helium contained
many common lines ; indeed at first the observed coin-
cidences were so remarkable that he came to the conclusion
that the connection was so close that atmospheric argon con-
tained a gas absent from the argon seen in his helium tube.

This statement was subsequently withdrawn, but the
compound nature both of argon and helium was suggested
by the fact that there were lines common to the two gases.
These lines were in the red ; one coincidence I found broke
down with moderate dispersion, the other yielded subse-
quently to the still greater dispersion employed by Drs.
Runge and Paschen. It may be also stated here that I have
not found a single coincidence between argon and any line
in the spectrum of any celestial body whatever. This
happens, as everybody knows, also in the case of oxygen,
nitrogen, chlorine, and the like.

THE CLEVEITE GAS A COMPOUND.

The first spectroscopic observations made it perfectly
obvious that the gas as obtained from uraninite is a mixture
of gases, that the gas which gives the yellow line is not an
isolated one, but is mixed up with other gases which give
other lines.

In May I wrote as follows : — 1

" The preliminary reconnaissance suggests that the gas
obtained from broggerite by my method is one of complex
origin.

1 Proc. R. S., Iviii., p. 114.

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 273

" I now proceed to show that the same conclusion holds
good for the gases obtained by Professors Ramsay and
Cleve from cleveite.

" For this purpose, as the final measures of the lines of
the gas as obtained from cleveite by Professors Ramsay and
Cleve have not yet been published, I take those given by
Crookes and Cleve, as observed by Thalen.

" The most definite and striking result so far obtained is
that in the spectra of the minerals giving the yellow line
I have so far examined, I have never once seen the lines
recorded by Crookes and Thalen in the blue. This demon-
strates that the gas obtained from certain specimens of
cleveite by chemical methods is vastly different from that
obtained by my method from certain specimens of brog-
gerite, and since, from the point of view of the blue lines,
the spectrum of the gas obtained from cleveite is more
complex than that of broggerite, the gas itself cannot be
more simple.

" Even the blue lines themselves, instead of appearing
en bloc, vary enormously in the sun, the appearances being

4922 (4921-3) = thirty times
4713 (47 1 2-5) = twice.

" These are not the only facts which can be adduced to
suggest that the gas from cleveite is as complex as that
from broggerite."

It is seen that quite early in the inquiry we had not only
spectroscopic evidence in the laboratory which was com-
plete in itself, but that the case was greatly strengthened
when the behaviour of the various lines in the sun and stars
was also brought into evidence.

In the first case we had the laboratory separation of D,
from the lines 5048, 5016, and 4922.

Later on in the same month I showed that the lines at
D3 and 447 behaved in one way, and that at 667 behaved
in another.

In order to test this view I made some observations
based on the following considerations : —

(1) In a simple gas like hydrogen, when the tension of
the electric current given by an induction coil is increased

274 SCIENCE PROGRESS.

by inserting first a jar and then an air-break into the circuit,
the effect is to increase the brilliancy and the breadth of all
the lines, the brilliancy and breadth being greatest when the
longest air-break is used.

(2) Contrariwise, when we are dealing with a known
compound gas ; at the lowest tension we may get the
complete spectrum of the compound without any trace of
its constituents, and we may then, by increasing the tension,
gradually bring in the lines of the constituents, until, when
complete dissociation is finally reached, the spectrum of the
compound itself disappears.

Working on these lines the spectrum of the spark at
atmospheric pressure passing through the gas or gases,
distilled from broggerite, has been studied with reference
to the special lines C (hydrogen), D3, 667, and 447.

The first result is that all the lines do not vary equally
as they should do if we were dealing with a simple gas.

The second result is that at the lowest tension 667 is
relatively more brilliant than the other lines ; on increasing
the tension C and D3 considerably increase their brilliancy,
667 relatively and absolutely becoming more feeble, while
447, seen easily as a narrow line at low tension, is almost
broadened out into invisibility as the tension is increased
in some of the tubes, or is greatly brightened as well as
broadened in others (Fig. 12).

4471

D3

5875.

c

6563 667.

1.

Mi

Fig. 12. — Diagram showing changes in intensities of lines brought about by varying the
tension of the spark, i. Without air-break. 2. With air-break.

The above observations were made with a battery of
five Grove cells ; the reduction of cells from 5 to 2 made
no difference in the phenomena except in reducing their
brilliancy.

Reasoning from the above observations it seems evident
that the effect of the higher tension is to break up a com-
pound or compounds, of which C, D3, and 447 represent
constituent elements ; while, at the same time, it would

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 275

appear that 667 represents a line of some compound which
is simultaneously dissociated.

The unequal behaviour of the lines has been further
noted in another experiment, in which the products of
distillation of broggerite were observed in a vacuum tube
and photographed at various stages. After the first heating
D3 and 447 1 were seen bright, before any lines other than
those of carbon and hydrogen made their appearance.
With continued heating 667, 5016, and 492 also appeared,
although there was no notable increase of brightness in the
yellow line ; still further heating introduced additional lines,
5048 and 6347.

These changes are represented graphically in the fol-
lowing diagram (Fig. 13).

D3

447. 492.501. 5876. 634 667.

504
Fig. 13. — Diagram showing order in which lines appear in spectrum of vacuum tube

when broggerite is heated.

It was recorded further that the yellow line was at times
dimmed, while the other lines were brightened.

In my second note, communicated to the Royal Society
on the 8th May, I stated that I had never once seen the
lines recorded by Thalen in the blue, at A 4922 and 4715.

It now seems possible that their absence from my
previous tubes was due to the fact that the heating of the
minerals was not sufficiently prolonged to bring out the
gases producing these lines.

It is perhaps to the similar high complexity of the gas
obtained from cleveite that the curious behaviour of a tube
which Professor Ramsay was so good as to send me, must
be ascribed. When I received it from him the glorious
yellow effulgence of the capillary while the current was
passing was a sight to see. But after this had gone on
for some time, while the coincidence of the yellow line with
D3 of the chromosphere was being inquired into, the lumi-
nosity of the tube was considerably reduced, and the colours

276 SCIENCE PROGRESS.

in the capillary and near the poles were changed. From
the capillary there was but a feeble glimmer, not of an
orange tint, while the orange tint was now observed near
the poles, the poles themselves being obscured by a coating
on the glass of brilliant metallic lustre.

After attempting in vain for some time to determine the
cause of the inversion of D3 and 447 in various photographs
I had obtained of the spectra of the products of distillation
of many minerals, it struck me that these results might be
associated with the phenomena exhibited by the tube, and
that one explanation would be rendered more probable if it
could be shown that the change in the illumination of the tube
was due to the formation of platinum compounds, platinum
poles being used. On 2 1st May I accordingly passed the cur-
rent and heated one of the poles, rapidly changing its direction
to assure the action of the negative pole, when the capillary
shortly gave a very strong spectrum of hydrogen, both lines
and structure. A gentle heat was continued for some time,
and apparently the pressure in the tube varied very con-
siderably, for as it cooled the hydrogen disappeared and the
D3 line shone out wTith its pristine brilliancy. The experi-
ment was repeated on 24th May, and similar phenomena
were observed.

Some little time after1 Professors Runge and Paschen,
from an entirely different standpoint, arrived at exactly the
same conclusion.

The employment of exposures extending over seven
hours has given a considerable extension in the number of
lines, and the bolometer has been called in to investigate
lines in the infra-red ; better still, they have employed well-
practised hands in searching for series of lines. Operating
by chemical means upon a crystal of cleveite free from any
other mineral, they have obtained a product so pure that
from these series there are no outstanding lines. Very
great weight, therefore, must be attached to their conclusions.

As a result of their investigations Drs. Runge and
Paschen stated that the gas given off even by a pure crystal

1 Nature, 26th September, 1895.

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 277

of cleveite is not simple. In their view the mixture consists
of two constituents.

This conclusion was arrived at from the following con-
siderations. " The wave-lengths A of the lines belonging to
the same series are always approximately connected by a
formula somewhat similar to Balmer's —

i/X = A - B/;//2 - C/m\

A determines the end of the series towards which the lines
approach for high values of m, but does not influence the
difference of wave-numbers of any two lines. B has nearly
the same value for all the series observed, and C may be
said to determine the spread of the series, corresponding
intervals between the wave-numbers being larger for larger
values of C. As B is approximately known two wave-
lengths of a series suffice to determine the constants A and
C, and thus to calculate approximately the wave-lengths of
the other lines. It was by this means that we succeeded in
disentangling the spectrum of the gas in cleveite, and
showing" its regularity.

"In the spectrum of many elements two series have been
observed for which A has the same value, so that they both
approach to the same limit. In all these cases the series
for which C has the smaller value, that is to say, which has
the smaller spread, is the stronger of the two. In the
spectrum of the gas in cleveite we have two instances of
the same occurrence. One of the two pairs of series, the
one to which the strong yellow double line belongs, consists
throughout of double lines whose wave-numbers seem to have
the same difference, while the lines of the other pair of series
appear to be all single. Lithium is an instance of a pair of
series of single lines approaching to the same limit. But
there are also many instances of two series of double lines
of equal difference of wave-numbers ending at the same
place as sodium, potassium, aluminium, etc. There are also
cases where the members of each series consist of triplets of
the same difference of wave-numbers, as in the spectrum of
magnesium, calcium, strontium, zinc, cadmium, mercury.
But there is no instance of an element whose spectrum
contains two pairs of series ending at the same place. This

278 SCIENCE PROGRESS.

suggested to us the idea that the two pairs of series belonged
to different elements. One of the two pairs being by far
the stronger, we assume that the stronger one of the two
remaining series belongs to the same element as the stronger
pair. We thus get two spectra consisting of three series
each, two series ending at the same place, and the third
leaping over the first two in large bounds and ending in the
more refrangible part of the spectrum. This third series we
suppose to be analogous to the so-called principal series in
the spectra of the alkalis, which show the same features.
It is not impossible, one may even say not unlikely, that
there are principal series in the spectra of the other elements.
But so far they have not been shown to exist.

" Each of our two spectra now shows a close analogy to
the spectra of the alkalis.

"We therefore believe the gas in cleveite to consist of
two, and not more than two, constituents."

To the one containing the line D3, which I discovered
in 1868, the name helium remains ; the other for the present
we may call " gas X V

The chief lines of these two constituents are as follows,
according to Runge and Paschen, the wave-lengths being
abridged to five figures.

i

Hi I ol

I II] L

8
If '

i !

~'^r

r 5

1L

Li

,r in.

1

j A

• .1

'

ttSTtTUCHY ■ CAS

1

j

i

\
1
J _

i
i

!

i

j

i

'-'

j

"** '

i

Fig. 14. — Runge and Paschen's results suggesting that cleveite gives off
two gases, each with three series of lines.

1 In the many comparisons I had to make, I soon found the incon-
venience of not having a name for the gas which gave 667, 501 and other
lines. When, therefore, Professors Runge and Paschen, who had endorsed

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 279

HELIUM.

1st Subordinate

2nd Subordinate

Principal Series.

Series.

Series.

2663-3

3456-9?

3481-6

2677-2

3461-4?

3490-8

2696-2

3466-0

3502-5

2723-3

347I-9

35I7-5

2763-9

3479'1

3537-0

2829-2

3487-9

3563-I

2945-2

3498-8

3733'0

3187-8

35I2'6

3867-6

3888-8

353o-6

4121-0

3554-6

4713-3

3587-4

7065-5

3634-4

3705-1

3819-8

4026-3

4471-6

5875-8

GAS X.

1st Subordinate

1
and Subordinate

Principal Series.

Series.

Series.

3176-6

3756-2

3770-7

3196-8

3768-9

3787-6

3211-6

3785-o

3838-2

323I*3

3805-9

3878-3

3258-3

3833-7

3936-0

3296-9

3872-0

4024-1

3354-7

3926-7

4169-1

3447-7

4009-4

44377

3613-8

4143-9

5047-8

3964-9

4388-1

7281-8

5oi5-7

4922*1
6678-4

my results, and had extended them, called upon me, I thought it right to
suggest to them that, sinking the priority of my own results, we should all
three combine in suggesting a name. Professor Runge (under date 20th
October) wrote me : " The inference that there are two gases is a spectro-
scopical one, being based on the investigation of the ' series '. Now, though
we think this basis quite sound, we must own that the conclusion rests on
induction. . . . For this reason we do not want to give a name to ' gas
X '." I have so far suggested no name, though Orionium and Asterium
have been in my mind.

280

SCIENCE PROGRESS.

More recently Professor Ramsay has abandoned his
view of the simple nature of the cleveite gas, and states
that from his experiments "there appears ground for the
supposition that helium is a mixture ".1

THE EXISTENCE OF THE NEW GASES IN CELESTIAL BODIES.

And now comes the great revelation, and it is this.
The majority of the lines classed as unknown in the spectra
of the Orion nebula, stars of Group III. and the sun are
really due to the cleveite gases.

The following table sets this result out. It will be seen
that of seventeen unknown lines, twelve have been run to
earth.

COMPARISON OF UNKNOWN {PREVIOUS TO HE. AND X)
LINES IN ORION NEBULA AND BELLA TRIX.

Orion Nebula.

Bellatrix and
Eclipse, 1893.

Origin.

Campbell.

Lockyer.

3869

*3869 (7)

t3867-5

(Falls

He.

3889

3888 (7)

3888onHe.)

He.

—

4°i 1 (3)

4009 (8;

X

4026

4026 (5)

4026 (10)

He.

—

4042 (1)

4041 (3)

Still Unknown

4067

4068 (3)

4°7° (3)

Still Unknown

4121

4121 (1)

4121-3(7)

He.

4H3

4143 (T)

4144 (8)

X

—

4168 (1)

4169 (5)

X

4265

4270 (3)

4268 (7)

Still Unknown

4389

439° (3)

4389 (8)

X

4472

4472 (7)

4472 (10)

He.

—

454° (3)

454i (1)

Still Unknown

—

4628 (3)

4630 (3)

Still Unknown

4714

47i6 (3)

47i5 (5)

He.

■ —

*4924 (5)

f4922-i (8)

X

5874

5875-8

5875-8

D3 He.

* Between these AA there are forty-two lines in the Orion photograph of which six are
known other than He. and X.

t Between these AA there are forty-five lines in the Bellatrix photograph of which
five are known other than He. and X.

The following tables give the complete list of lines
and the celestial body in which they have been traced.

1 Nature, vol. liii., p. 598.

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 281

In the tables, under "sun," C, followed by a number,
indicates the frequency as given by Young ; E indicates the
lines photographed during the eclipse of 1893. Under
"star or nebula" the references are to the tables given in
my memoir on the nebula of Orion {Phil. Trans., vol.
clxxxvi., 1895, P- 86 et seq. N = Nebula of Orion).

HELIUM.

I 1220.

Sun.

Star or Nebula.

3889

C E

N. III. y

3188

2945

2829

2764

'*

2723

2696

2677

5876

C 100 E

4472

C 100 E

4026

C 25 E

3820

E

a Cygni

3705^

3634

3537

3555

35I3

3499

>*

3488

3479

3472

3466

346iy

7066

C 100

47i3

C 2 E

4121

E

N. a Cygni

3868

?

3777

E

Bellatrix

3652

3599

3567

3537

35i7

'*

35°3

349i

3482,

* Means that these lines are out of the range of my observations.

20

282

SCIENCE PROGRESS.

GASX.

Sun.

Star or Nebula.

5016

C 30 E

3965

?

III. y

36M>

E

3448

3355

3297

.*

3258

3231

32i3J

6678

C 25

4922

C 30 E

4388

E

N. III. y

4144

E

III. y

4009

III. y

3927

Bellatrix

3872

Bellatrix

3833

E

Hid byH. line

3806

Bellatrix

3785*

7282

5048

C 2

4438

Bellatrix

4169

Bellatrix

4024

?

N. III. y

3936

Hid in K.

3878

C E

a Cygni

3838

C E

a Cygni

3803"-

* Means that these lines are out of the range of my observations.

The annexed reproduction of a photograph of Bellatrix
will show how striking has been the result of the discovery
so far as stellar spectra are concerned.

Hydrogen, helium and gas X are thus proved to be
those elements which are, we may say, completely repre-
sented in the hottest stars and in the hottest part of the
sun that we can get at. Here then, in 1895, we have
abundant confirmation of the views I put forward in
1868 as to the close connection between helium and
hydrogen.

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 283

EFFECTS OF DIFFUSION.

A diffusion experiment described in their paper enabled
Messrs. Runge and Paschen to go a stage farther, and to

x

a

31

0

■

M

(

Ln

J

3889

"|

H

3*

- -!: "

3926

W

*"0

rt
0

.

3964

rf

c

; ... _

t

3968

3
0

•;'■•■" HhSFv

i-h

«

4009

rt

;>

"rr

4026

p"

r*

K

-1

.• • ^S^f&v^i

rfi

\

3*

O

4101
4121

<

5'

era

1.

4143

cr 3*

...

4169

r* rt

p ,_.

S'5'

D- tzi

^KHvH

3>o

1 ■

-

- iy: '-y;~; y'y-^.

3^

3 g-

1

; .,.''■

5'°

*

SL 3

,

4340

Cfl ^

" 3

el-

-

4388

'.

''■"•■

s'

0

,- ■

*

;■

4437

C/3

rt

k

3

> z*

-v

• -

— U. ■ -

447 2

3*

n'

I •

s*

.

3*

p

<

re

'". -!

r:^,#*i^f':-'i

cr

n>

'*.

rt

<

3

*

t-t

M

P

O

rt

» - ! •'.

47*3

p.

rf

0

•

'

r+

%

W38&f&'

3"

£$£a, •' "-

rt

OQ

4860

P

W

rt

C/3

<-$ w w TJ

announce that of their two constituents the gas-giving D3
was the heavier one. They also add :—

" From the fact that the second set of series is on the

284 SCIENCE PROGRESS.

whole situated more to the refrangible part of the spectrum,
one may, independently of the diffusion experiment, con-
clude that the element corresponding to the second set is the
heavier of the two ".

As they themselves pointed out, however, the result was
not final, because the pressures were not the same. I have
recently made some experiments in which the pressures
remain the same.

An U tube was taken, and at the bend was fixed a
plaster of Paris plug about 1*5 cm. thick; in one of the
limbs two platinum wires were inserted. The plug was
saturated with hydrogen to free it from air ; the tube was
then plunged into a mercury trough, and fixed upright with
the limbs full of mercury. Into the leg (A) with the plati-
num wires a small quantity of hydrogen was passed, and as
soon after as possible another small quantity of a mixture
of helium and hydrogen from samarskite was put up the
other limb (B) of the U tube.

Immediately after the helium was passed into the limb
(B) spectroscopic observations were made of the gas in the
limb (A) ; D3 was already visible, and there was no trace of
50157. This result seems to clearly indicate that if a true
diffusion of one constituent takes place, the component which
gives D3 is lighter than the one which gives the lines at
wave-length 50157.

Although this result is opposed to the statement made
by Runge and Paschen, it is entirely in harmony with the
solar and stellar results.

In support of this I may instance that of the cleveite
lines associated with hydrogen in the chromosphere and the
stars of Group III. y ; those allied to D3 are much stronger
than those belonging to the series of which 50157 forms
part.

MINERALS EXAMINED.

So far I have worked upon some seventy minerals, and
I have found the orange line in sixteen.

The following are the minerals, etc., which have been

THE GROWTH OF OUR KNOWLEDGE OF HELIUM. 285

investigated ; those which give the D. line beino- marked
with an asterisk : —

*.Eschynite.

Almandine.

Anglesite.

Anhydrite.

Augite.

Barytes.
*Broggerite.

Bronzite.

Calco-uranite.

Cassiterite.

Celestine.

Chalk.

Charnockite.

Chromite.
*Cleveite.

Columbke.

Crocidolite.

Cupro-uranite.
*Eliasite.

Enstatite.
*Euxenite.
*Fergusonite.

Franklinite.

Gadolinite.

Gahnite.

Geikielite.

Gneiss.

Granite.

Graphite.
*Gummite.

Haematite.
*Hielmite.

Hornblende.

Hypersthene.

Ilmenite.

Iridosmine.
Kielhanite.

Kyanite.

Ludvvigite.

Magnesium.

Magnetite.

Manganese Nodule.

Minium.
*Monazite.

Obsidian.

Olivine.

Olivine-Enstatite.
*Orangeite.

Orthite.

Pitchblende.

Plumbic Ochre.
*Polycrase.
*Pyrochlore.

Quartz.

Red Clay.

Rhodonite.
*Samarskite.

Schurlomite.

Sphene.

Staurolite.

Thorite.
*Thoro-gummite.
*Uraninite.

Uranocircite.

Uranophase.

Wulfenite.

Wolfram.

Xenotine.
*Yttro-Gummite.

J. Norman Lockyer.

INSULAR FLORAS.

PART VI. (a).

IN the preceding articles I have briefly reviewed the
literature relating to Insular Floras which has appeared
during the last decade, and I have extracted therefrom the
principal or most interesting facts, which I have given with
some comments of my own. That I have been able to do
this with some profit is largely due to the advantages I have
enjoyed through the kindness of the Director of the Royal
Gardens, Kew. Since the publication in 1885 of my first
essay on this subject, in the Botany of the Voyage of H. M.S.
" Challenger" all or nearly all collections of insular plants
received at Kew have passed through my hands for determina-
tion and reporting on ; and I have also been favoured with
many notes and criticisms by travellers and other persons
interested in plant distribution. I propose therefore to
enter into a short recapitulation and discussion of the main
facts thus accumulated ; but before doing- so I will refer to
some more or less important contributions to the subject
that have come to light during the progress of the present
series of articles.1

It will be convenient to take the islands in the same
geographical order previously followed (1), beginning with
Polynesia.

There are some interesting recent contributions to the
flora of Polynesia, taking the designation in its widest
sense ; but no one has yet attempted to bring together what is
known, or ascertainable from materials preserved in herbaria,
of the vegetation of the numerous small coral islands and
groups of islands, more or less recently annexed by, or taken
under the protection of, Great Britain. This the writer is
engaged upon, and some particulars thus acquired may be

1 A review of the additional literature having extended beyond what
was expected, the discussion referred to will form the subject of a conclud-
ing article.

INSULAR FLORAS. 287

utilised here in dealing with the literature of the subject.
Some years ago Mr. J. T. Arundel delivered a lecture at
San Francisco, before the Geographical Society of the
Pacific, on the Phcenix Group and other islands of the
Pacific, and he has since published it (2) with additional
notes. Mr. Arundel writes from actual experience, having
visited a large number of the most remote islets of the
Pacific and collected samples of their scanty floras, which
were determined for him at Kew, where the specimens are
preserved. Unfortunately several of the names of the
plants in his list have undergone such a transformation as
to be almost unrecognisable.

Besides the Phcenix Group, which was under his personal
control, Mr. Arundel visited such out-of-the-way islands as
Starbuck, Caroline (not the Caroline Group), Fanning,
Maiden, Palmerston and Ducie. Mr. Arundel describes
Starbuck and Caroline Islands as examples of two kinds of
very small islands common in the Pacific, though not con-
fined to it. The former represents those consisting of an
unbroken mass which is treeless, and indeed almost devoid
of vegetation ; and the latter is a typical coral atoll, con-
sisting of a ring of islets encircling a central lagoon, and
supporting a relatively luxuriant vegetation. Starbuck is
very scantily furnished with vegetation, only about half a
dozen species being represented. The principal plants are
Lepidium piscidium and Sida fallax ; both of wide range
in Polynesia. Caroline Island claims a little more atten-
tion, because its history, position, conformation, meteorology,
botany and zoology have been very fully worked out and
illustrated. In 1883 this island was selected by the Ameri-
cans, by the British, and by the French as the most suitable
spot for observing the total eclipse of the sun. The Ameri-
can party was relatively numerous, and they drew up a
somewhat elaborate report (3), illustrated chiefly by prints
from photographs taken by the two gentlemen constituting
the English party. These illustrations give an excellent
idea of the form and vegetation of an atoll, including a
bird's eye view, which enables us, better than any description
could, to realise its smallness and isolation. Caroline Island

288 SCIENCE PROGRESS.

is situated in almost exactly 150° W. longitude and io° S.
latitude, and is distant, according to Mr. Arundel, about
400 miles from Tahiti, the nearest island of considerable
size — say a third larger than the Isle of Wight ; and 420
from Starbuck. Although in most parts well clothed with
vegetation, this vegetation consists of very few, perhaps
not more than twenty, species of vascular plants. Several
others now exist, either as the remains of cultivation or
accidental introduction ; and the abundance of the cocoanut
palm is due to planting, which has now been in operation
for some years. Whether the cocoanut existed in the
island on the first advent of man there is no evidence to
show ; but there are trees of other kinds of large size, as
depicted and described in the report referred to. They are:
Calophyllum Inophylliim (Guttiferse), Morinda citrifolia
(Rubiaceae), Cordia subcordata (Boragineae), Pisonia grandis
(Nyetaginaceae), and a screw pine, probably the widely spread
Pandanus odoratissi?nus. One of the illustrations is a most
effective representation of a group of screw pines. The
Cordia is perhaps the commonest tree, and is most con-
spicuous, having a spreading crown with branches down to
the ground. Pisojiia grandis is described as forty or fifty
feet high, with a trunk four feet in diameter ; dimensions
one would hardly have expected. I have drawn some-
what freely from this report, because it is by far the most
instructive known to me.

A more recent contribution to island literature by Mr.
C. M. Woodford (4) is equally deserving of attention,
though wanting illustrations. It deals with the Gilbert
Archipelago, one of the most remarkable of the numerous
groups in the Eastern Pacific. There are sixteen islands,
not counting the islets of the atolls, forming a chain, trend-
ing from north-west to south-east and extending from about
3° north to 30 south latitude in 1730 to 1 77° east longitude.
Eleven out of the sixteen are of atoll formation, and the
largest of them is little more than twenty miles long and
twenty feet high in the highest part. They are mostly
inhabited, and the population half a century ago was
estimated at 50,000, though it has since dwindled down to

INSULAR FLORAS. 289

probably a quarter of that number. The presence of so
large a population must have had some modifying influence
on the vegetation ; yet not to the extent that might have
been expected, because there is little cultivation, the natives
living largely on fish, with which the waters swarm. Mr.
Woodford says : " The islands are clothed from end to end
with a dense growth of cocoanut palms and other vegeta-
tion, and present a beautiful appearance when approaching
from the sea. The reefs and lagoons teem with fish, thus
enabling the islands to support a population which for
their land area was at one time equalled in no part ot the
world."

Mr. Woodford gives a list of the plants compiled from
observations on the islands he visited, which he believes is
nearly complete. As I am able to supplement it by a few
additional species in the Kew Herbarium, chiefly collected
by the Rev. Mr. Whitmee, and also to supply specific names
in some cases where he gives only the generic, I will give a
list of all the vascular plants known to inhabit the group, as
a sample of the typical coral island flora. Calopkyllum
Inophyllum (Guttiferae), Sidafallax (Malvaceae), Triiunfetta
procumbens (Tiliaceae), Tribulus cistoides (Zygophyllacese),
Pemphis acidula (Lytheraceae), Rhizophora mubronata
(Rhizophoraceae), Guettarda speciosa and Morinda citrifolia
(Rubiaceae), Sccevola Kcenigii (Goodeniaceae), Tournefortia
argentea (Boraginaceae), Pisonia biennis and Boerhaavia
^fksYZ (Nyctaginaceae), Euphorbia Atoto? (Euphorbiaceae),
Ficus tinctoria (Moraceae), Crinum pedunculatum ? (Am-
aryllidaceae), Cocos nucifera (Palmaceae), Pandanus odora-
tissimus (Pandanaceae), Fimbristylis glomerata (Cyperaceae),
Lepturus repens (Gramineae), and Polypodium Phymatodes
(Filices) — just a score of species, it will be seen, belonging
to as many different genera, and to eighteen different natural
'orders of the most diverse habit and structure. They
are almost without exception plants of general distribution
in tropical oceanic islands and on the sea-shores of the
continents. The majority of them indeed inhabit the
smaller remote islands of the tropical parts of the Indian
Ocean. I will only add here that their seeds are such as

2go SCIENCE PROGRESS.

are transported by oceanic currents, birds, and winds, with-
out destroying their vitality. In another article I pro-
pose discussing these agents of dispersal in some detail.
The absence from the above list of the two largest natural
orders — Leguminosae and Compositse — may cause some
surprise, especially as the seeds of many of the former bear
long immersion in salt water with impunity, and the pappose
achenes of the latter are often, it is assumed, conveved
lont{ distances bv wind. Le^uminos£e are rare in all
oceanic islands, both coral and volcanic ; but Composite,
on the other hand, are characteristic of many volcanic
islands, the Galapagos and St. Helena, for example.

The distribution of the plants of the Tonga or Friendly
Islands has been worked out by the writer (5), and a few
of the most interesting facts may be repeated here. This
group lies to the south-east of Fiji, between 180 and 230
south latitude, and 1730 and 176° west longitude, and com-
prises both volcanic and coral islands ; some of the former
being considerably larger than those of the Gilbert Group,
and rise to altitudes of 500 to 3000 feet. Fuller informa-
tion on the geology of the islands will be found in an article
(6) by Mr. J. J. Lister. But although the Tonga Islands
are considerably larger than the Gilbert Islands, it is more
in land area and altitude than external dimensions, and
it is due partly to the absence of central lagoons. Ton-
gatabu in the south, the largest of the group, is about
twenty-two miles in its greatest length, and is composed
entirely of coral limestone. This island is the best known
botanically ; but Mr. ]. J. Lister, whose collections were
worked out for my paper referred to above, thoroughly ex-
plored the neighbouring smaller, though more elevated,
Eua, which gave a considerable number of additional
species. Since the publication of my paper, Kew has
acquired a collection of dried plants made by Mr. C. S.
Crosby in the Vavau cluster in the north. This collection
has not yet been thoroughly worked out, but although
it doubtless contains some additions, they will not be of a
character to modify what has been written respecting the
affinities of the flora of the whole group. The total num-

INSULAR FLORAS. 291

ber of assumed indigenous species of vascular plants in
my enumeration is 290, whereof 246 have a westward, and
220 have an eastward extension in Polynesia; 138 are
Australasian (Australia, New Zealand and outlying islands),
162 are Malayan, and at least 150 have a wider range
either in the Old or New World, or in both. From the
foregoing figures it will be seen that the Bora of the
Tonga Islands is largely composed, like the very small one
of the Gilbert Islands, of species of wide distribution.
Indeed no genus is peculiar to the group, and only ten
species so far as our present knowledge goes are endemic,
and a more complete exploration of the Fiji Islands and
other neighbouring groups may reduce this number. The
290 species of the Tongan flora represent no fewer than
202 genera and seventy-nine natural orders out of the 202
recognised in Bentham and Hooker's Genera Plantarum.
The proportions are 2*55 genera to an order, and 1 '43 species
to a genus in the Tongan flora. In the flora of the world
the proportions I obtained by a very rough calculation are
37 '5° genera to an order, and 12*65 species to a genus.
Taking the number of Tongan species (138) which extend
to Australasia, one might overestimate the affinities, be-
cause, as a matter of fact, a large proportion of these species
have a wide range. Indeed only a dozen species have
decidedly Australasian connections. These are : Melicytus
ramiflorus, Ratonia stipitata, Metrosideros polymorpha,
Jasmirmm simplicifolium, Hoya australis, Iponuea congesta,
Pisonia inermis, Peperomia leptostackya, Euphorbia Spar-
mannii, Ficus aspera, Podocarpus elata and Pteris comans.
It will be perceived that the connections are specific rather
than generic. But the most significant facts brought out
in the paper under consideration are two, namely, the
large proportion of species — upwards of a third — peculiar to
Polynesia, and the strongly Malayan character of the flora,
generally, of the Tonga, Fiji and Samoa Islands.

Several additional small contributions to the flora of
the Solomon Islands have appeared (7), including some
highly interesting novelties collected by the officers of
H.M.S. Penguin, and the Rev. R. B. Comins. Excellent

292 SCIENCE PROGRESS.

photographs of the singular new genus Sararanga
(Pandanaceae) have been received at Kew, as well as ripe
fruit in spirit, which will enable me to add to my published
description, though not to complete it, because the male
inflorescence is still unknown. Two species of Begonia, an
Oxymitra (Anonacese) with flowers nearly nine inches long,
a singular Tabernce Montana having a twisted fruit, and
the anomalous genus Lophopyxis (8) are among the latest
additions to the flora of the Solomon Islands. The last is
doubtingly placed in the Euphorbiaceae by Sir Joseph
Hooker, and it has since been twice described (9 and 10),
and placed in different natural orders, namely, Combretopsis
(Olacinese) and Treubia (Saxifragaceae). There are two
or three very closely allied species or races inhabiting
Malacca, Ceram, New Guinea, and the Solomon Islands.
I may refer in passing to a zoological paper (11) in which
the author puts forward the theory of a former connection
of the Solomon, Fiji, New Hebrides, Loyalty, New-
Caledonia, Norfolk and New Zealand Islands with New
Guinea, but not with Australia. That there was, in the
remote past, a greater land area in this region seems
highly probable, but the relationships are so complex that
fuller data are required to afford a solution of the problem.
The present flora of Lord Howe Island, described a few
pages forward, does not favour Mr. Hedley's views in their
entirety on this point.

In my reference to the flora of Christmas Island (12) I
overlooked a paper that supplemented mine to some extent
(13), especially in relation to the vegetation.

Dr. Trimen (14) has published two more volumes of
his admirable flora of Ceylon, bringing it down to the end
of the Balanophoraceae, following the arrangement of
Bentham and Hooker's Genera Plantarum. The same
author has drawn up a provisional list (15) of Maldive
plants ; the first, I believe, that has appeared. As might
be expected there is no endemic element, and the vegeta-
tion is an assemblage of the ubiquitous coral island plants
and weeds of cultivation. Dr. Trimen makes no mention of
the Cocos maldivica or Coco-de-mer (Lodoicea sey die liar inn) \

INSULAR FLORAS. 293

but, although it is improbable that this palm ever grew in
the Maldive Islands, something yet remains to be done to
complete its history. John de Barros, a Portuguese
author, is thus quoted (16) by the writer of an article on
these islands : —

"Their productions he also enumerates minutely, especially
the coconut, both of the ordinary kind and of that called
coco-de-mer, almost peculiar to the Seychelles, the seed of
which appears to have been borne thence to the Maldivas
by the currents of the ocean ".

Since the publication of my notes on the flora of New
Zealand and the outlying islands (17) several interesting
papers on the subject have appeared, though there is only
one of sufficient importance to call for more than brief
mention. But first the minor ones. Mr. F. Kirk is the
author (18) of a series of monographs treating of the
genera Gentiaua, Colobatttktis, and Gunnera, as re-
presented in the New Zealand region, besides descriptions
of a number of new species belonging to various natural
orders. The forms of Gentiana are numerous, and the
species exceedingly difficult of delimitation. Kirk defines
ten species, and about half of them comprise several
varieties. They are spread all over New Zealand, except
the extreme north, and they extend to the Chatham,
Antipodes, Auckland and Campbell Islands ; but hitherto
no species has been found in Macquarie Island, the southern-
most of these islands. They chiefly inhabit the mountains,
in alpine and subalpine situations, and the sea-coast ; four
out of the ten, it is stated, not being found out of the reach
of the sea-spray. They all belong to one group, char-
acterised by having pentamerous flowers, unappendaged
corollas, and versatile anthers. White is the prevailing
colour of all the species, though some of them occasionally
exhibit various shades, mostly dull, of red, purple, and violet,
and more rarely a pale yellow. This is in direct contrast to
the behaviour of the northern species, speaking generally, and
we are indebted to Mr. Kirk for the observation. Colo-
banthus (Caryophyllaceae) is one of those densely tufted
moss-like genera of which there are representatives in

294 SCIENCE PROGRESS.

various natural orders. It is one of the very few genera
common to Australasia, to the Antarctic, and other southern
islands, and the Andes, and confined to these regions. One
species, C. quitensis, ranges from the mountains of Mexico
to Cape Horn and reappears in New Zealand. Kirk also
records it from Amsterdam Island, but that seems to in-
volve two errors, for, so far as our data at Kew go, C.
diffusus inhabits St. Paul, and no species is found in the
neighbouring island of Amsterdam. One species, C.
Billardieri, is found in the Alps of Victoria, in Tasmania, New
Zealand, and the small islands southward to Macquarie. Two
Falkland Islands species also recur in South Georgia, the
southern insular limit of phanerogamic vegetation in the Pata-
gonian region, if we except a grass, Aira antarctica, collected
by Dr. Eights in the South Shetlands, about 620 S. lat., or
8° south of South Georgia. Kirk enumerates and de-
scribes ten species of Colobanthas from the New Zealand
region, including four proposed new ones.

Gunnera (Haloragidacea^) has a similar range to that
of Colobantkus, save that it does not reach the colder limits
either in America or the New Zealand region. Kirk
brings up the species of the latter region to nine, four of
which are new.

W. Colenso, D. Petrie, and H. C. Field also describe
a few novelties (19), and the first named gives a charming
description of his travels and botanising in the romantic
country around Hawke's Bay, upwards of fifty years
ago.

The one paper which I propose to discuss a little more
in detail is devoted to the natural history of Macquarie
Island (20), the most southerly speck of land in the New Zea-
land region known to support phanerogamic vegetation. It
is in the same latitude (540 S.) as South Georgia in American
waters, the flora of which I have described (21), where a
list is given of the vascular plants inhabiting the island.
They are separated from each other by about 164° of
longitude, which in this latitude means, in round numbers,
5875 geographical miles ; yet, as previously stated, nine
out of thirteen of the vascular plants found in South

INSULAR FLORAS. 295

Georgia also occur in some of the southern islands in the
New Zealand region. Later on I shall have something-
to say, or rather repeat, in explanation of this fact. It
should be noted that these islands are in about the same
latitude as York in England ; yet the climate is now so
severe in South Georgia and other conditions are so un-
favourable to vegetation that the flora is perhaps poorer
than in the highest northern latitudes yet explored, and
entirely wanting the colour characteristic of many northern
flowers. For example, such charmingly beautiful plants as
Papaver nudicaule, Silene acaulis, Saxifraga oppositifolia
and Epilobium latifolium are found north of the eightieth
parallel ; whereas the showiest flowers in South Georgia are
those of a very small buttercup, so small indeed that they want
finding. The flora of Macquarie Island is, however, not
altogether devoid of colour, as witness Pleurophyllum ; and
Stilbocarpa is remarkable for its large rhubarb-like leaves.

Macquarie Island is between twenty and twenty-five
miles long and five or six miles across in its broadest part.
It is generally hilly, though the hills are nowhere above
800 feet. The following is a list of the vascular plants
recorded by Mr. Hamilton (20), who visited the island
early in 1894. I may mention that I had most of these
plants under observation (22), and I do not agree in every
instance with his and Mr. Kirk's (23) determinations ; but
the divergencies are unimportant ; and there are several
corrections of the names given in previously published lists.
Ranunculus ci-assipes, Cardaminc hirsuta, var. corymbosa,
Colobanthus muscoides, C. Billardieri, Stellaria decipiens,
Mont ia font ana, Aceena Sanguisorbcz, A. adscendens, Calli-
triche a7itarctica. Epilobium nummularifolium, E. lin-
nceoides, Azorella Selago, Stilbocarpa polaris, Coprosma
repens, Cotula plumosa, Pleurophyllum Hookerii, Uncinia
nervosa, Luztila criuita, Deschampsia Hookeri, D. penicil-
lata, Poa foliosa, P. Hamiltonii, Agrostis antarctica,
Festuca contracta, Aspidium aculeatum, var. vest it um Poly-
podium aust?'ale, Lomaria alpina and Lycopodium Billar-
dieri, var. varium. The last named one would have
hardly expected to find in so high a latitude, where the

296 SCIENCE PROGRESS.

only woody plant is the small creeping Coprosma repens,
because it usually grows on trees. A re-examination
of a very small collection of Macquarie Island plants
sent by Mr. Fraser of the Sydney Botanic Garden to the
late Sir William Hooker, about sixty years ago, has led to
the discovery of Lycopodium Selago, associated with Azor-
ella Selago, a very similar plant in external appearance. In
addition to the foregoing there are three colonised vascular
plants, namely, Stellaria media, Cerastium triviale and Poa
annua ; and Mr. Hamilton states that he also collected
Tillcea muscosa and two sedges, but the specimens were
lost. If we except three imperfectly known grasses, which
Mr. Kirk has described as new (24), there are no endemic
plants in the island. The vascular cryptogams are all
widely spread, two of them recurring in the northern hemi-
sphere. Of the flowering plants upwards of half are confined to
the New Zealand region, and the rest have a wider range.
Stilbocarpa polaris ( Aral iacese) and Pleurophyllum Hookerii
(Composite) are the two most remarkable and most con-
spicuous plants in this meagre flora ; the former having
large rhubarb-like leaves, and the latter silky, silvery leaves
and handsome purple flower-heads in long racemes. Colo-
banthus, Azorella, Acczna and Uncinia are equally charac-
teristic in the South American region.

Quite recently a fresh account of Lord Howe, Pit-
cairn and Norfolk Islands has appeared (25), but it con-
tains nothing new on the botany of these islands. Special
stress is laid on the beauty of the vegetation of Howe
Island, where palms and tree ferns abound, and fig-trees of
the banyan type attain dimensions hardly exceeded else-
where. What is known, however, of the botany of this
interesting island has appeared in Government Reports and
scattered in a variety of publications (26-29) of limited
circulation. It is true that Sir F. von Mueller long ago
published (30) a bare list of all the plants known to him
from the island, but it is incomplete, and supplies no in-
formation beyond the names of the plants. This being so,
I am preparing a detailed account of the flora of this island
with a view to publication elsewhere. I may here give,

INSULAR FLORAS. 297

however, some particulars gleaned from the publications
referred to, though they are mostly anterior to the date
(1885) to which I have limited myself generally in these
articles, adding a few remarks of my own on the distribu-
tion of the plants.

Lord Howe Island is of small extent and peculiar con-
formation, situated about 300 miles from the coast of
New South Wales in 310 35' S. lat. It is seven miles
long with an average breadth of one mile, and the steep
circular flat-topped elevations rise to a height of nearly
3000 feet. Norfolk Island, the nearest land to the north-
east, is about 500 miles distant, and New Zealand, to the
south-east, somewhat farther off. The island is of volcanic
origin, consisting of three basaltic masses connected by
coral-sand rock. About 165 species of indigenous flower-
ing plants are known, and forty-eight ferns and lycopods.
As already indicated palms form a conspicuous feature in
the scenery. There are four species, all endemic, and
they have been very much named, though three out of
the four are well known under the generic name of Kentia.
They are K. Belmoreana, K. Canterburyana and K. For-
steriana — names familiar to many persons, as they have
long been favourite palms in cultivation on account of their
elegance and hardiness. A tall and graceful specimen of
K. Forsteriana is one of the finest ornaments of the central
part of the palm-house at Kew. The fact of there being
a good market for the seeds of these insular palms has led
to considerable destruction of the trees to obtain them ; but
I believe the Government of New South Wales has made
it a punishable offence to destroy trees on public territory.
Beccari (31) has founded the genus Howea for them, which,
if accepted, is the only endemic one. There are also four
indigenous tree ferns, three of which are endemic. But the
banyan trees {Fiats columnaris) are perhaps the most
striking objects in the vegetation. Several appear in the
photographs illustrating Wilson's Report, one of which is
said to cover an area of three acres ! Morcea Robinsoniana
is an outlying gigantic member of an African genus of

Irideae very closely allied to Iris itself. It is known as the

21

298 SCIENCE PROGRESS.

wedding-flower, and there is a fine specimen of it at the
south end of the cactus-house at Kew. Carmichcelia exul
(Leguminosae) is the only species of a considerable genus,
with this exception, not known to inhabit any other country
than New Zealand. There are other connections with the
flora of the latter country, but they are mostly such as extend
to Australia as well. Pimelea longifolia and the handsome
sedge, Gahnia xantkocarpa, are apparently exceptions. In
round numbers 25 per cent, of the species of flowering plants
of Lord Howe Island are endemic, and 62 per cent, are
common to Australia, many of these having a wider
range. A few are common only to Australia, New Zealand,
and Norfolk Island. The shrubby violaceous genus
Hymenanthera is an example. The gum trees {Eucalyptus)
of Australia are represented by the endemic Acicalyptus
Fullagari, a small Fijian genus differing from Eucalyptus 'in
having a calyptrate calyx-limb and separate petals. Two
other conspicuous trees in the endemic element are Draco-
phyllum Fitzgeraldii (Epacridese) and the screw-pine, Pan-
danus Forsteri. The former is a tree, said to be the largest
in the order, attaining the height of fifty to sixty feet. It has
the foliage and aspect of a monocotyledon rather than of a
dicotyledon. One characteristic Australasian type we miss
in the Lord Howe Island flora, and that is Cor dy line.

When reviewing (32) the newer literature relating to
the flora of the Galapagos Islands I found little to add to
what had been done by Darwin, Hooker and Andersson ;
merely mentioning the visit of the United States ship
Albatross, and Dr. G. Baur's theory of the origin of the
fauna and flora. Since then an account of Dr. Baur's
botanical collections has been published (33), and the sub-
stance has also appeared in an English journal (34), and
Dr. Baur himself has written (35) and lectured (36) in
defence of his theory of the origin of this group of islands.
As previously stated, he contends that the evidence points
to the present condition being the result of subsidence ;
that the islands were formerly connected with each other
and at a still earlier period with continental America.
Although this theory has been derided, I think the biologi-

INSULAR FLORAS. 299

cal data strongly favour its correctness, and the soundings
given in the map accompanying Agassiz's report (2,7) of
the Albatross expedition show a relatively shallow area
in which the Galapagos Islands are situated, and which
extends eastward to the mainland of Veraguas. Probably
the separation would be greatly anterior to the segregation
of the West Indian Islands.

In the Botany of the Challenger expedition (38) I
attempted a rough classification of islands in relation to the
composition of their floras. These are defined as follows :
1, Vegetation comprising a large endemic element including
distinct generic types ; 2, vegetation comprising a small,
chiefly endemic element, the derivation of which is easily
traced ; and 3, vegetation containing no endemic element.
Without due consideration the Galapagos were referred to
the first category. Sir Joseph Hooker (39) fully realised
the absolute American affinities of the flora ; but he analysed
and discussed it as a derived one rather than as a remnant.
Darwin, through some misinterpretation of the statistics sup-
plied to him, fell into a singular error respecting the generic
endemic element in the Galapagos (40). Referring to
the Compositse, he says : " There are twenty-one species,
of which twenty are peculiar to this archipelago ; these
belong to twelve genera, and of these genera no less than
ten are confined to the archipelago ! " How this error arose
it is impossible to say, but as a matter of fact the statement
quoted is wrong (and was wrong at the time it was written)
in all its details. With regard to assumed endemic genera
of Compositae, five were founded on galapageian plants,
namely, Microcoecia and Desmocephalum, since reduced to
Elvira ; Macrcea to Lipochczta ; and Scalesia and Lecocar-
pus are so near to Mirasolia and Melampodinm respectively
that the late Mr. Bentham gave it as his opinion that they
might well be reduced. Two genera from these islands
belonging to other orders have also been reduced. These
are Galapogoa = Coldtnia (Boraginacae), and Dictyocalyx
= Cacabus (Solanacese) ; and Pleuropetalum (Amarantaceas)
has since been found in several localities in Western
America. Taking this view of their affinities, there is not

3oo SCIENCE PROGRESS.

a single genus of flowering plants endemic in the Galapagos ;
but each island has its distinct species. Briefly put then,
the genera are the same in all the islands, and the genera
are American ; whereas a large proportion of the species
are peculiar to each island, though they are not so ex-
clusively confined to single islands as Darwin supposed.
On this point he says (41) : " Again Euphorbia, a mundane
or widely distributed genus, has here eight species of which
seven are confined to the archipelago, and not one found on
any two islands. Acalypha and Borreria, both mundane
genera, have respectively six and seven species, neither of
which genera has the same species on two islands, except
in the case of one species of Borreria." Dr. Baur's
recent explorations necessitate a considerable modification
of this statement ; yet in a sense they confirm and empha-
sise it. Baur himself deals more particularly with the fauna
(36) in illustration of this phenomenon. More than 400
specimens of the lizard genus Tropidurus were collected,
and in the result he found that "each island possessed only
a single species ; all the individuals of an island belonged
to one species ; and nearly every island had its peculiar
species or race ".

The botanists who worked out Dr. Baur's collections
selected Euphorbia viminea (33) as an example of a plant
exhibiting racial differences in each of the eight islands,
where it is now known to occur. The genera Acalypha
and Borreria are cited as other instances. On the other
hand, Euphorbia articulata, which was collected on four
different islands, showed no such tendency.

In a former article in this journal (32) I mentioned the
fact that huge branching Cactacese form one of the most
striking features in the lower zone of the vegetation of the
Galapagos, and I have elsewhere (42) given some par-
ticulars of what is known, and how little is known of these
Cactaceae ; and I may repeat here that specimens of only
one species have, so far as I can ascertain, been brought
away from the islands. These were brought to this country
by Darwin, and published by Henslow (43) under the
name of Opuntia galapageia. This species is remarkable

INSULAR FLORAS. 301

in the genus for its very small flowers, which are only about
three-quarters of an inch in diameter, and also for the small
number of petals ; but as the figure was made from dried
specimens, it may be inaccurate in some details. In the
same place it is mentioned that a species of Cereus was
common in the island, but was not found in flower.

Darwin himself specially alludes (44) to the prominent
feature these Cactacese are in the landscape, and likewise
to the fact that they grow in the rough lava where there is
absolutely no other phanerogamic vegetation. He further
points out their importance as food for the gigantic tor-
toises and land lizards. They are also a source of water
during the severe droughts, which often parch the lower
zone.

Subsequent travellers have dwelt upon the part the
Cactacese play in the biology of the island, and Andersson,
a botanist who visited the islands in 1852, states (45) that
he observed four or five species, but had time neither to
prepare specimens nor sketch the plants.

My note on the subject in Nature came under Dr.
Baur's notice, and he forwarded me two photographs, one re-
presenting a fine example of an arboreous Opuntia of great
size, and the other a view embracing a number of large
Cerei, together with a transcript of his notes on the subject
in a paper (46) which I had not seen. He was struck by
the difference in the appearance of the Optmtice on the
different islands, and observed that the large Opuntia has
a different habit on nearly every island. Thus, on Barring-
ton, Indefatigable and South Albemarle, it develops a
very tall stem ; on Charles and Hood a relatively short
but thicker stem ; on Jervis a very short stem, branch-
ing from very near the ground, and on Tower Island
it forms no stem at all, and appears as a dwarf bush.
Dr. Baur attributes these modifications to the varying degrees
of humidity, the greatest development occurring in the driest
climate. In the lower region of South Albemarle, up to
about 500 feet, the Opuntia is very common, attaining a
large size, the largest being about twenty feet high, with a
trunk two feet in diameter. " In old trees the bark looks

302 SCIENCE PROGRESS.

very much like that of a pine, and peels off in very thin
sheets."

The common Cereus, which strongly resembles C.
peruvianus, attains almost the same dimensions ; but this
is all we know about it at present, and there is clearly
much more botanical work to be done in the Galapagos
before the subject is exhausted. It may be of interest to
add that no species of cactus inhabits the island of Juan
Fernandez, but this may be ascribed to climatic differences.
Indeed, so far as is known, none of the other Pacific American
islands, at any considerable distance from the coast, support
any members of the order, though Malpelo, for example,
is barren enough to give them a chance of flourishing.

Another remarkable element in the flora of the Galapagos
is the relatively large number of species of the small order
Amarantacese. About fifteen species are now known to in-
habit the islands, and twelve of them are endemic. They
belong mainly to the genera Telautkera, Alternanthera,
and Froelichia.

Concerning the flora of the Arctic Islands in relation to the
adjacent continents, I have to add a few references (47-48)
to works of older date than my paper (49), and a few recent
ones of unusual interest. Mr. Trevor- Battye's account of
the vegetation of Kolguev Island (50) and Colonel Feilden's
contributions on the subject (51-52) rank first among these.
The former noted ninety-five species of phanerogamia in
Kolguev, and his observations on the vegetation are of
great value. About a score of the plants recorded by
Ruprecht (53) were not found, and Trevor-Battye remarks
on the absence of Saxifraga oppositifolia, Mertensia maritima
and Ledum palustre. Colonel Feilden's short paper on
Spitsbergen plants, as well as his remarks on mild arctic
climates, is worthy of attention on account of his experience.
The only information I have found (54) respecting the
vegetation of Einsamkeit Island is that there is no grass
carpet, and it is added that there is a great quantity of drift-
wood, sometimes far inland. A new list (55) of Iceland
and Faeroe plants does not claim to be anything more than
a contribution to local distribution.

INSULAR FLORAS. 303

There is little new literature relating to the Atlantic
Islands, but Sir Joseph Hooker's comparison (56)
of the Maroccan and Canarian floras was overlooked by me
when reviewing the writings of Dr. Christ. In an article
(57) of more recent publication, the latter gives expression
to a considerable modification of his views on the affinities
of the Canarian flora. He now recognises a much more
intimate connection with the old African flora. But I must
not reopen the subject here.

One important contribution (58) to the flora of the West
Indies has appeared. This part consists of a critical
elaboration of the Myrtaceae, than which there was probably
no group of plants more in need of revision. It is some-
what appalling to see such familiar trees as the allspice and
clove with a page and half of synonyms each ; yet it is
very useful, historically, as well as for practical purposes, to
have them brought together.

W. BOTTING HEMSLEY.

(To be continued.}

THE PRESENT POSITION OF THE CELL-
THEORY.

(CONCLUSION.)

THUS far I have tried to rehabilitate the cell as a vital
unit. I have now to deal with the further question as
to the part played by the cell in the composition of the higher
animals and plants. In the earlier part of this essay I
stated that Mr. Adam Sedgwick denied in toto the proposi-
tion that "the elementary parts of all tissues are composed
of cells ". Since writing those words, Mr. Sedgwick's reply
to my previously published criticisms has appeared,1 and I
find that I have made a mistake. For he does not deny
the proposition, but says: ''The assertion that organisms
present a constitution which may be described as cellular is
not a theory at all ; it is — having first agreed as to the
meaning and use of the word cell — a statement of fact and
no more a theory than is the assertion that sunlight is com-
posed of all the colours of the spectrum ". I can only beg
Mr. Sedgwick's pardon. I certainly was led to suppose
from his earlier writings that he regards the cell as a
nonentity, in so far as it may be considered to be the
ultimate structural unit of the metazoa, and I recoiled from
his suggestion that the essence of development lay in "a multi-
plication of nuclei and a specialisation of tracts and vacuoles
in a continuous mass of vacuolated protoplasm ".

Mr. Sedgwick now explains that he objects, not to the
statement that tissues are composed of cells — or, in his own
words, that they have a composition which may be described
as cellular — but to the statement that an individual meta-
zoon is an aggregate of lesser individuals, or, as it has often
been expressed, a cell colony or cell republic. I have else-
where— and as Mr. Sedgwick well says, after great effort —
come to agree with him on this point, for a careful survey
of a considerable range of facts led me to the conviction

1 Adam Sedgwick, "Further Remarks on the Cell-Theory, with a Reply
to Mr. Bourne," Quart, four. Micr. Sci., vol. xxxviii., p. 331, 1895.

THE PRESENT POSITION OF CELL-THEORY. 305

that the idea of a cell republic was inappropriate. Such
being the case I would willingly have buried the hatchet,
but when I had already dug the hole to bury it in, my hand
was stayed by some criticisms on his views and on mine
which have just been published in a contemporary periodi-
cal.1 These criticisms have restored to me the conviction
which I held when I ventured to write a criticism of Mr.
Sedgwick's views ; a conviction that, as he originally
expressed them, they were calculated to mislead and to do
harm to the very cause whose interests he was desirous to
promote. As he has lately explained that he did not mean
what I supposed him to mean, there is no need for quarrel-
ling any further with him, but he will himself allow that I
was amply justified when I gave the following as a not
unfair statement of his position. That from the connection
known to exist between some cells composing adult tissues,
there is an antecedent probability that similar connections
exist between all cells composing all tissues ; and this
probability is heightened by observations made on the
development of Peripatus, by the fact that the so-called
mesenchyme cells in Avian and Selachian embryoes are
continuous and not isolated as was once supposed, and by
a study of the developing nerves of Elasmobranchs. And
that it follows from this that the morphological concept of a
cell so far from being of primary is altogether of secondary
importance, and that progress in the knowledge of structure
is impossible so long as men persistently regard cells as the
fundamental structural units on which the phenomena mani-
fested by organised beings depend. The true method of
inquiry must be a study of the growth, extension, vacuolation
and specialisation of the living substance protoplasm.

He has been understood by others as I understood him,
and indeed he had so expressed himself that he could
scarcely have been understood otherwise. What I had
anticipated has happened. Persons, ready to grasp at
novel ideas, have said in their hearts : "Tush, there is no cell !
There are protoplasmic masses which may contain one or
many nuclei ; the mass is of no importance, it is scarcely

x Natural Science, vol. vii., No. 46, December, 1S95.

306 SCIENCE PROGRESS.

more than the medium in which the nucleus lives, and
through which it exhibits its powers. The nucleus may
move about in the mass, acquiring ' spheres of influence '
at its halting places, and so producing the vital phenomena.
It is the nucleus which is the vital unit, and there is no
bond between nucleus and cytoplasm which shall compel
us to regard their union as the necessary condition of living
individuality."

I have made use of my own expressions, but if this is not
the plain meaning of the short editorial entitled "The
Reign of the Nucleus" in the January number of Natural
Science, what is ?

The writer of the editorial is so captivated with the pros-
pect opened up by his interpretation — a perfectly legitimate
interpretation — of Mr. Sedgwick's writings, that he forthwith
abolishes the existence of cells altogether and talks glibly
of " protoplasmic masses," ignoring the fact that the masses
in question are divided up into corpuscles. Following up
his theme of protoplasmic masses dominated by nuclei, he
lightly dismisses the arguments which I put forward,
saying that the segmentations of Nereis, Unio, etc., exhibit
nuclear lineage rather than cell lineage (who could
hold such an opinion after a careful study of Wilson and
Lillie's figures ?), and winds up with the following astonish-
ing piece of criticism : " In drawing an argument for the
cell-theory from the definite places assigned to cells in
development Bourne seems to us to have overlooked the
experiments of Wilson, Driesch and Hertwig, who have
shown that the nuclei may be moved about in the proto-
plasmic mass almost as freely as a ' heap of billiard balls
may roll over each other ' ". I rubbed my eyes and
wondered. I thought I knew the works of Driesch,
Hertwig and Wilson pretty well, and that I had considered
them carefully, and I had certainly regarded them as strong
evidence in favour of the cell-theory as I conceived of it.
A short search soon hit upon the passages which are
professedly quoted. First for Driesch : x " Die Furchungs-

1 Hans Driesch, Entwicklungmechanischse Studien, iv., Zeitschrift fUr
IViss. Zoologie, vol. Iv., 1893.

THE PRESENT POSITION OF CELL-THEORY. 307

kugeln der Echiniden als ein gleichartiges Material
anzusehen sind, welches Man in beliebiger Weise, wie
einen Haufen Kugeln durch einander werfen kann, ohne
dass seine normale Entwicklungsfahigkeit darunter im
Mindesten leidet ". (The segmentation spheres of Echinids
are to be regarded as a homogeneous material which one may
roll amongst one another at will like a heap of balls, without
thereby destroying in the least their capacity for develop-
ment.) No hint whatever of rolling the nuclei through the
protoplasmic mass. The statement is made of Furchungs-
kugeln, that is of cells, and it is the cells that one may roll
about like balls. Not a bad argument for my contention,
that the blastomeres of many developing ova are disjunct.
If there were any doubt as to Driesch's words a study of
figures 39-68 which illustrate his paper would satisfy the
most exacting. The blastomeres are unusually distinct
from one another, especially in the embryoes illustrated by
figs. 63 and 67. Now for Hertwig:1 "Bei den verschiedenen
Modificationen des Furchungsplasma werden die aus dem
ersten Furchungskern durch aufeinanderfolgendeTheilungen
erzeugten Kerngenerationen Theilen des Dotters, die in Eir-
aum eine sehr verschiedene Lage einnehmen, zuoetheilt und
mit ihnem zu einem zellkorper verbunden. Die Kerne wer-
den in Eiraum wie ein Haufen von Kugeln durch einander
gewurfelt." This is a very complicated German sentence
and might well lead to a misunderstanding, but it comes out
all right in plain English. "In the various modifications of
the divisional processes the nuclear generations, which are
produced by successive divisions from the segmentation
nucleus, are assigned to a portion of the yolk which occupies
very different positions within the limits of the egg, and are
bound with it to form a cell body. The nuclei are rolled
one over another within the limits of the egg like a heap of
balls." This passage is a summary of preceding state-
ments and inferences, and it might be held to bear a very
different meaning to that which it does bear ; the illustration

1 O. Hertwig, " Ueber den Werth der ersten Furchungszellen fur die
Organbildung der Embryo," Arch, fur Mikr. A nat., vol. xlii., p. 662, 1893.

308 SCIENCE PROGRESS.

of the heap of balls is a very loose one. To understand
the meaning of the summary one must turn to pp. 678-685
of the same memoir, which consist of a section entitled
" Erklarung des abnormen Furchungsverlaufes ". There
we learn, as we had previously learnt from Driesch, that
the divisional planes of segmenting ova are determined by
the direction of the nuclear spindles and that the orientation
of the first nuclear spindle is determined by the character of
the body of the ovum and its contents. The ova of Echinus
are homogeneous throughout, and orientation of the first
nuclear spindle is a chance affair. But the ovum of the
Frog is not homogeneous ; it consists of a smaller cap of
protoplasm resting on a large body of yolk, and the nucleus
lying in the cap of protoplasm, the direction of the first
nuclear spindle is determined by its relations to the more
active yolk on the one hand, and the denser food yolk on
the other. The relations of the food yolk and protoplasm
are changed by the pressure applied during the experiments
and the changes are different according as the pressure is
applied vertically or horizontally. Hence the direction of
the first and the succeeding nuclear spindles is changed
in different senses, according to the pressure employed. As
the divisional planes are always at right angles to the
nuclear spindles, the positions of the two first and the suc-
ceeding blastomeres differ according as the pressure applied
is vertical, horizontal, oblique, or circumferential. One may
in fact cause the blastomeres and their contained nuclei to
take up what position one will by varying the direction of
the pressure. In this sense, and in this sense only, can one
speak of rolling the nuclei about like balls. Not a word about
a protoplasmic mass through which the nuclei are caused to
roll. On the contrary, a great deal about planes of division
and splitting up of the egg into corpuscles round the nuclei.
It only requires a glance at Hertwig's figures and diagrams
to show that the blastomeres are as distinct during abnor-
mal division as during normal division, and that there is not
at any time any question of a "protoplasmic mass," a cir-
cumstance which has been well understood by everybody
who has taken the trouble to read his memoir carefully.

THE PRESENT POSITION OF CELL-THEORY. 309

Most of the experiments of Wilson, Hertwig and
Driesch were of a different kind. They isolated the blas-
tomeres by gentle shaking. Driesch is very careful to say
gentle ; rough shaking destroyed the individual blastomeres.
Things which are so loosely united as to be separated thus
easily from one another scarcely suggest the nature of a
coherent protoplasmic mass.

The criticism falls entirely to the ground and one can
only wonder how any one could have had the temerity to
make it. The very objections urged to my views are but
additional evidence in support of them, and I was well
aware that the evidence existed when I wrote, but I had to
be as brief as possible, and did not refer to it. My state-
ment that it is very clearly established that there are
numerous cases in which there is not "a primitive con-
tinuity which has never been broken" is abundantly
justified. Mr. Sedgwick wonders why I emphasised the
distinction and complete isolation of the cells formed by
the segmentation of the egg. The reason is surely clear
enough. Because he suggested, in no uncertain manner in
his earlier writings, that the connections between adult cells
were due to a primitive continuity which had never been
broken, and that those who urged that such connections
were secondary were in the wrong. This suggestion was
contrary to fact, and it was my object to show that it was.
I did not contradict myself when I stated immediately
afterwards that the organism cannot be considered to consist
of independent life units, for I went on to show that the
cell-republic theory is also contrary to fact, and must there-
fore be condemned. If a contradiction exists, it exists in
nature, and after we have ascertained the facts the next
thing is to try to explain this seeming contradiction. Mr.
Sedgwick says that he does not think it possible to do so,
until we acquire some more understanding of the relative
functions of nuclei and protoplasm. Possibly he is right,
yet I think that an attempt may be made, and if the explana-
tion is after all not very satisfactory yet some service may
be done, for we may arrive at more distinct ideas about
fundamental points, and we must gain much by a careful

310 SCIENCE PROGRESS.

classification of the facts. Such a classification has yet to
be made. So long as a theory is dominant, as the cell-
republic theory was, exceptions and difficulties are glossed
over, or are explained away by a phrase. When I made a
vigorous onslaught on Mr. Sedgwick, I was afraid that he
wished to substitute King Stork for King Log and bring us
under the domination of a new theory of his own. His
reply to my strictures and his careful exposition of his own
standpoint are reassuring on this point, and if I exceeded the
limits of courtesy in my article, I did so under a misunder-
standing and express my regret for it. Mr. Sedgwick has
done a great service in breaking the bonds of the old theory.
Now the question is, having got our liberty, what are we
going to do with it ?

Firstly, I think, we have got to make up our minds as
to what we mean by a vital unit.

In the first part of this essay I stated that the cell is par
excellence the vital unit, by which I meant nothing more
than that it is the simplest form of material aggregate in
which individual life is possible. There would seem to be
no objection to such an application of the word unit. But
the term unit is a relative one, and its correlative is
multiple. If, therefore, we see that the developing embryoes
of many animals and likewise the tissues of the adult forms
are made up of structures which we must call cells, and if
we call the cell a vital unit, we are obliged to conclude that
the animals in question are composed of an aggregate of
vital units, which leads us directly to the doctrine of a cell-
republic. Thus at the outset we are confronted by the
great difficulty that what experience teaches us to deny
reason compels us to affirm.

There must be a flaw somewhere, either in the facts or
in the reasoning. There can hardly be any doubt about
the facts ; the flaw therefore must be in the reasoning, and
I do not doubt that it consists in our insistence on applying
the idea of a unit to biological facts. As Whewell would
have said, the idea is inappropriate. The term unit, as we
use it in Biology, conveys a double meaning. On the one
hand, it borrows part of its meaning from the idea of num-

THE PRESENT POSITION OF CELL-THEORY. 311

ber, and to this extent the term is used in an equivalent
sense to that in which it is used in Physics. But put side
by side such expressions as unit of mass or unit of time with
the expression unit of life, and a little reflection will suffice
to show that the sense is inappropriate. Nor is the case
made better if we compare the unit of life with the chemical
unit. The value of the latter consists essentially in this,
that it is a means of dealing numerically with chemical facts,
and experience shows that ideas of number are very
appropriate to chemical facts. With life the case is very
different. In the present state of our knowledge the con-
nection between life and number is of the slenderest kind,
and it is insufficient to justify our applying numerical ideas
to vital phenomena.

The other sense in which the term unit is used in
Biology is purely subjective. It stands to express our idea
of individuality, an idea which is founded on our own states
of consciousness. It is unnecessary for me to dilate upon
the controversies which have raged round this idea of in-
dividuality in its application to the animal kingdom. The
most acute reasoners are not agreed upon the precise
point where individuality ceases to belong to parts and
belongs to the whole even in some of the simpler colonial
organisms, and in such cases as the Siphonophora a satis-
factory solution of the problem appears to be hopeless.

But these cases are simple in comparison with that
which we are now discussing. If then we cannot agree
about the limit of individuality in colonial organisms, how
are we likely to agree about the same thing in the case of
organic structure in general ?

There is this to be said, however, that for us the test of
individuality should be a biological test, and the idea is there-
fore more appropriate to the question than the numerical idea
just spoken of. It was, no doubt, the recognition of its
propriety which lent such force to Schwann's argument,
" since it may be proved that some cells, which do not
differ from the rest in their mode of growth, are developed
independently, we must ascribe to all cells an independent
vitality ".

3i2 SCIENCE PROGRESS.

Hence, as it seems to me, whilst we can and ought to
get rid of the numerical idea expressed by the word unit, we
cannot get altogether rid of the idea of individuality, and
we must do our best to bring it into harmony with the facts.

Since there is an inseparable connection between the
idea of number and the word unit, we ought to get rid of
the expression " unit of life," and use some other term
which shall denote alike the simplest and the most com-
plex of living beings. The word organism I have aheady
objected to because of its double connotation — would it not
be better to make use of such a word as "biont," which is
as nearly as possible the equivalent of the German " Leben-
diges " ? Anything which leads or is capable of leading an
independent individual life is a biont. Thus a cell may be
a biont, as in the case of the protozoa, or it may be a con-
stituent part of a biont, as in the case of the metazoa. In
any case the cell is the simplest form of biont known, for if
we 2"o behind the cell we have structures which are not
capable of leading an independent individual life.

But a cell in the case of metazoa, or the nucleus and
other structures in the case of protozoa, and unicellular
plants are things which, whilst they participate in, and con-
tribute to life, and to that extent may be considered as living,
are not in themselves capable of independent individual
existence. They may be called metabionts.

The terminology suggested may not be perfect, but by
the use of it or of something equivalent we may shake our-
selves free of the false ideas which have clustered about
individual life units, and start with a new hope on an inquiry
into the nature and growth of bionts.

An essential part of our conception of a biont is the
union of two substances, cytoplasm and nuclein. It does
not matter, for present purposes, that we know nothing
exact about these two substances, and still less of the
manner in which they operate together to produce the
phenomena of life. It suffices that we know that there are
bionts whose structure is so simple that we can affirm no-
thing more of them than that they consist of cytoplasm and
nuclein, e.g., Bacteria, Yeast, Oscillaria, etc.

THE PRESENT POSITION OF CELL-THEORY. 313

Within the limits of the protozoa we study many kinds
of bionts which, whilst retaining great simplicity of structure,
have advanced far beyond the stage represented by these
simple forms.

The most important as well as the most striking
structural advance is the formation of a nucleus. The
nuclein which was, in the simplest bionts, distributed
through the protoplasm, is aggregated to form a compact
body, which from its structure and behaviour may be re-
garded as a metabiont, as also may the part from which it
was segregated, the cytoplasm. The steps which lead up
to the segregation of the nucleus are obscure, but there are
very good grounds for saying that the nucleus, when formed,
is connected, in some manner unknown to us, with the
transmission of the so-called historic qualities of the biont.
In any case it plays a leading part in reproduction, and the
steps from the condition of diffused nuclein to centralised
nuclein are suggested by the infusorian Holosticha scutelhim,
which ordinarily has no definite nucleus, but contains
numerous chromatin particles scattered throughout its sub-
stance. Previous to reproduction by division the scattered
particles are drawn together and unite to form a centralised
nucleus, which divides in a normal manner and breaks up
again into particles in the offspring.1

Besides the nucleus many other structural advances are
to be noted in protozoa and in unicellular plants ; some
must be regarded as metabionts, e.g., chlorophyll corpuscles
and chromatophores of various kinds, many kinds of granules,
etc. Other structures cannot be regarded as belonging to
the same category, e.g., cilia, contractile fibres, etc. We
may for the present purpose leave both cases out of con-
sideration, for it is the nucleus and the part it plays as an
essential constituent of the biont which most concerns us.

We have as yet very obscure notions about the co-opera-
tion of nucleus and cytoplasm in the production of vital
phenomena. But, putting aside the views of those who
postulate the existence of minute vital units, and speak of

1 Aug. Gruber, " Ueber vielkernige Protozoa," Biol. Centralblatt, iv., p.
170. See also the same author, Zeit.fiir Wiss. Zool., xli., p. 186.

22

314 SCIENCE PROGRESS.

an emanation of specialised biophors from the nucleus into
the cytoplasm, there is a general agreement that the co-
operation is of the nature of a complex exchange of
chemical material. If this be the case, the rate of exchange
must be the measure of vital activity, and it is clear that
the rate of exchange will be greatest in immediate proximity
to the nucleus and will become increasingly less the greater
the distance from the nucleus. At a certain distance, which
might be called the limit of nuclear influence, the rate of
exchange will be reduced to zero. We see that in the
protozoa the forms which have a single nucleus are small,
and we may say, in consequence of the foregoing- considera-
tions, that their size is determined by the limits of nuclear
influence. But many protozoa are multinuclear, and I
believe that there is no exception to the rule that protozoa
of relatively large size are also multinuclear. Such is
obviously the case in such forms as Radiolaria, Actino-
sphserium, Pelomyxa, the Myxomycetes and others. From
a consideration of all the facts of the case we may legiti-
mately infer that in any given biont growth beyond
certain limits is incompatible with a uninuclear condition,
and that further growth involves multiplication of the
nucleus, which may have as consequences: (i) discon-
tinuous growth, which in its simplest form is reproduction
by binary fission : (2) continuous growth, in which the
nucleus is multiplied so that all parts of the enlarged cyto-
plasm may receive an equal share of nuclear influence.
There are numerous cases in which, as I pointed out before,
the two conditions are combined. There is a ccenocytial r
stage of considerable duration, followed by reproduction
(or discontinuous growth).

The next phase is the formation of a biont of consider-
able size, in which very numerous nuclei are arranged in
definite manner in a continuous mass of protoplasm. Such
a condition is represented by the Cceloblastas, and also in the

1 When in my earlier essay I coined the word hypopolycytial I was
not aware that Professor Vines had applied the term ccenocytial to the
Cceloblastse. His term has the priority and is more euphonious, so I adopt
it instead of my own.

THE PRESENT POSITION OF CELL-THEORY. 315

growing tissues of many animals and plants, as for instance
in the embryoes of many Arthropods, in the endosperm of
Phanerogams, etc. The condition may be permanent, as
in the case of the Cceloblastae, or non-permanent, as in the
other cases. But in both instances there is a difference
from the ccenocytial condition observed in Protozoa, namely,
that the multiplication of the nucleus does not lead to re-
production in the form of the splitting up of the biont into
as many new bionts as there are nuclei.

In a ccenocytial biont of appreciable size the relations
of the various parts to external conditions will tend to be-
come different, and differences of chemical constitution will
be set up in the different regions exposed to different con-
ditions. We can see that this is the case in Botrydium, in
which root and shoot are plainly marked off from one
another, and better still in Caulerpa, in Codium, and in
many of the Moulds. Differences in chemical constitution
thus induced will mean difference in exchange between
nucleus and cytoplasm, and we may infer that, in accordance
with these differences, the cytoplasm within the limit of
influence of any one nucleus will in time assume a con-
stitution so different from that of the adjacent cytoplasm as
to become sharply marked off from it. It will then acquire
its own surface tension — the first step towards a cell wall—
and will be a separate corpuscle containing a nucleus, in
fact a cell. Such a cell however has not come into being as
an individual unit joined to its like, either phylogenetically
or ontogenetically, but it has from the first formed a part
of an organic whole, of which it is nothing more than a
specialised component part.

One looks naturally for evidence of this mode of forma-
tion of cellular structure in developing Metazoa. The best
evidence is to be found, I think, in the segmentation and
formation of the layers in many Ccelenterata. In some
Ccelenterata — for example, in Renilla — the nucleus divides
without accompanying division of the cytoplasm until eight
or sixteen nuclei are present, and then the cytoplasm
divides and eight or sixteen cells are formed. But of more
importance than this is the formation of the layers. From

316 SCIENCE PROGRESS.

the considerations stated above we should expect that the
changes in chemical composition of the cytoplasm and the
correlated changes in the nucleus, in other words the dif-
ferentiation, would first become manifest in the peripheral
parts of the growing ccenocyte, and that we should have a
stage in which there was a cellular external layer and a
ccenocytial internal mass. We find that in fact in the
embryoes of many Ccelenterates the outer layer is divided
up early into sharply defined cells at an early period, whilst
the central cells retain the character of a ccenocytium ; at
most the cell outlines of the internal mass are confused and
indistinct.

We see also that in the growing tissues of the embryoes
of higher animals the embryonic tissue is not cellular but is
a ccenocytium, for example, the mesoblast of Avian and
Selachian embryoes and of the Rabbit. It is only at a later
stage when different relations to other parts of the body
have been acquired and new exchanges of material are
forced upon the growing mass, that the continuous mass of
cytoplasm is split up into corpuscles, each of which, in my
view, corresponds to the limit of influence of a nucleus.

On the other hand we have the undoubted fact that in
many organisms there is no ccenocytial phase in develop-
ment, but the cytoplasm surrounding the nuclei as they are
successively formed is immediately marked off into definite
corpuscles, so that the whole process of development
suggests the formation of an aggregate of bionts derived by
division from a single parental biont. An explanation of
this fact presents many difficulties, and I have not now
the space to discuss these difficulties and to show that,
obscure as the subject still is, there is ground for supposing
that the difficulties are chiefly due to the prepossession
which exists in most minds in favour of the independent
life unit theory. I hinted in my previous paper (loc. ciL, p.
171) that the discrete condition of the blastomeres of so
many embryoes may be connected with the fact that they
are, from the very outset, specialised. This means that as
the nucleus is in some way associated with the transmission
of historic qualities, these qualities may be located in special

THE PRESENT POSITION OF CELL-THEORY. 317

parts of the nucleus, and on division, some of the daughter
nuclei may possess one set, others may possess another set
of " qualities ". By " qualities " I conceive that we mean
different chemical constitutions, and it would follow that the
daughter nuclei, being of diverse chemical constitutions,
would react in diverse manners on the adjacent protoplasm
and would each cause the delimitation of a territory of
cytoplasm within the limits of its own sphere of influence ;
in other words, cell bodies would be formed round nuclei of
different chemical constitutions.

There is, however, yet another consideration to be taken
into account. As Hertwig has shown, the cytoplasm in
many ova is not homogeneous but is obviously separable
into tracts of unquestionably different chemical constitution.
This is conspicuously evident in the ova of Amphibia. As
the nucleus divides, its products come into relation with
different kinds of cytoplasm and the exchanges between
nucleus and cytoplasm will be different in different places
within the limits of the egg. Arguing on the same prin-
ciples as before, we may attribute the successive formation
of discrete blastomeres to this factor as much as to the
separation in the course of division of different qualities
contained in the egg nucleus, and according as one leans
towards an epigenetic or an evolutionary theory of develop-
ment so will one be disposed to lay more stress on the
one factor or the other. There is this much to be said,
that the most remarkable cell-lineages (which are only
traceable when the blastomeres are discrete) have been
observed in ova which contain a considerable proportion of
yolk, which is not evenly distributed throughout the egg,
and it is suggestive that segmentation in all cases leads to
the segregation of corpuscles richer in yolk from corpuscles
poorer in yolk — in fact to the segregation of materials of
diverse chemical constitution.

Tempting as it is to pursue this subject further, I must
not attempt to do it now. But as I have claimed that the
views which I have tentatively put forward are agreeable
to the facts which we are in possession of, I may well give
a short summary of the facts which I have relied upon.

318 SCIENCE PROGRESS.

( i ) The co-existence of two substances at least, nuclein
and cytoplasm, is requisite for life. (This is an inference,
strictly speaking, and not a fact ; but I think that it may be
considered a legitimate inference from what we know of the
structure of the lowest bionts, and from the experiments of
Nussbaum, Gruber, Verworn and others.)

(2) The existence of bionts, such as Bacteria, in which
we are unable to distinguish more than these two sub-
stances. (This is a fact, which lends material support to
the above inference.)

(3) The existence of bionts in which nuclein and cyto-
plasm are not indefinitely intermingled, but the former is
segregated in the form of particles scattered through the
protoplasm, e.g., Trachelocerca phcenicopterus and Chcenia
teres. (We gather from this fact that the two chemical
substances tend to become separated from one another.)

(4) The temporary aggregation of nuclein particles to
form a centralised nucleus for the purpose of the repro-
ductive act, e.g., Holosticha scutellwm. (We infer from this
that there is some connection, at present hidden from us,
between the nucleus and the reproductive act.)

(5) The existence of many bionts in which the nuclein
is concentrated to form a nucleus. (We infer that this
is a grade of permanent differentiation arising out of
the previous temporary grade.)

(6) The existence of many nuclei in all bionts which,
whilst still undivided as regards their cytoplasm, attain to a
certain size. (From this we infer that the " limit of nuclear
influence " cannot extend through a large mass of cyto-
plasm.)

(7) The origin of "cellular" tissues from a ccenocytial
mass, e.g., the endosperm of Phanerogams; the neural
crest of certain Vertebrate embryoes ; the embryoes of
Arthropods; the mesoblast of many Vertebrates, etc. (From
this we infer that the cells composing many tissues of higher
animals are not to be regarded as bionts, but are secondarily
derived during the growth and extension of the parts of a
single biont.)

This re'sume suffices I think to show that this at least

THE PRESENT POSITION OF CELL-THEORY. 319

may be claimed for the views which I have put forward.
They are founded strictly on the facts, and they do not
depend on the assumption of any kind of hypothetical units
of which the nature and even the very existence is entirely
beyond our ken.

Since I have not been able to develop my views, I
cannot but expect that they will be subject to considerable
modification and even to entire overthrow. They form at
least an attempt to classify and colligate the various pheno-
mena which seem to be germane to the subject, and I have
collected and compared a much larger body of facts than I
am here able to refer to, without finding any which are
contradictory to my ideas. That my ideas are somewhat
indistinct need not, at present, be urged as an objection, for
indistinctness is not necessarily a sign of falsity. The cell-
republic theory was not wanting in distinctness, but
it was inappropriate to the facts. I only claim that my
ideas are appropriate, and I shall hope to give them more
distinctness on a future occasion.

In the meantime I leave out of consideration a large
question, concerning which I think it scarcely possible to
give a satisfactory account, in this standing in opposition to
Mr. Sedgwick, who thinks that which I have attempted to
be impossible, but offers a solution of that which I think
scarcely possible.

The question is, how are we to account for that pheno-
menon which I have described as a progress from the state
of an independent corpuscle, through a state of many coherent
or continuous or conjunct interdependent corpuscles, back
again to the state of a single independent corpuscle ?

Mr. Sedgwick's solution is this : that the unicellular
form is assumed by metazoa in order that conjugation may
be possible. The single independent corpuscle which re-
curs in the cycle is the sexual cell, and the essential feature
of sexual reproduction is the conjugation of reproductive
cells. The unicellular phase is only assumed in sexual, not
in asexual reproduction, and this is to be explained by the
consideration that conjugation is as necessary in metazoan
life as in protozoan life, but that conjugation between the

320 SCIENCE PROGRESS.

ordinary forms of metazoa is impossible for mechanical
reasons, and therefore special individuals of a form simple
enough to admit of conjugation are produced. These
special individuals are the ovum and spermatozoon.

The explanation is extremely ingenious and there is
nothing unreasonable in it, but one cannot say that it is
altogether acceptable at first sight. It would have been
more satisfying if Mr. Sedgwick had marshalled some of
the facts relative to the sexual reproduction of some of the
lowest multicellular organisms and had shown their rela-
tion to his suggestion. A difficulty which at once occurs
to me is that in many plants asexual reproduction is
effected through the agency of a single cell. In fact,
before one can accept any solution of the question one
requires a very extensive and careful survey of all the facts
known about the reproduction of the lower plants. They
afford examples of every conceivable grade of the reproduc-
tive processes, and, once one begins to look into the subject,
hints as to the parting of the ways of sexual and asexual
reproduction occur to one at every step. The pity is that
the mere zoologist, who does not find such a fruitful field in
his own territory, is obliged to disinter the facts from the
load which the peculiarities of botanical terminology have
heaped upon them.

It is quite possible, however, that such a survey would
afford strong support to Mr. Sedgwick's opinions, and if it
should do so they would in no way be inconsistent with
the ideas which I have put forward, but would rather sup-
port them.

A word in conclusion for those who will reproach me
for having attempted to frame a chemico-physical theory
of organic growth, and for having used such phrases as
" complex chemical constitution," " exchange of chemical
material," etc., without assigning any distinct meaning
to them. I admit that our knowledge on the subject
is rather inadequate, and that I have used obscure phrases
to express relations which are in themselves obscure. If
one attempts to lift the veil of obscurity one must inevitably

THE PRESENT POSITION OF CELL-THEORY. 321

call hypothesis to aid, and it has been my object to avoid
the use of hypothesis where I could do without it. It is,
however, legitimate to frame an argument which, while it
agrees with the lessons of experience, is ultimately based
upon hypothetical considerations, provided always that those
considerations are consistent with the accepted teaching of
the sciences whose aid is invoked.

Any attempt whatever to find an explanation of vital
phenomena ends in an appeal to chemistry and physics.
Knowing as we do that the elements of which organic
bodies are composed are not different from those which
occur in the inorganic world, we cannot refuse to acknow-
ledge that vital processes are in the end chemico-physical
processes, and this much is conceded by every author of a
theory of vital units. The difficulty which they have to
face is the same as that which I have to face, and is not one
whit the less because it is compressed into the limits of
a biophor, whereas I would allow it the limits of a cell.
Can we frame any distinct ideas of these chemico-physical
processes ? Not very distinct ideas, perhaps, yet we can
supplement the lack of positive evidence by analogies and
illustrations involving the same ideas as those which are
current in the physical world.

It was Professor W. K. Clifford, I think, who first drew
a graphic picture of the molecular forces which are at work
in any chemical compound, by describing the atoms as
linked to one another and dancing a sort of merry-go-round
within circumscribed limits. We may carry on the illustra-
tion, which, fanciful though it may seem, is supported by
physical and mathematical considerations. A biont is a
great organised war dance, performed by a whole army
corps. The individuals composing each company are the
atoms, they are linked to one another by companies and
each company dances its own figure. Every company is a
molecule, and every company dance is but a part of a larger
dance, in which the companies act in relation to one another
as the individuals act in the company dance. The larger
dances are regimental dances and every regiment is a
micella. The regimental dances are but parts of still larger

322 SCIENCE PROGRESS.

brigade dances, and the brigade dances are but part of the
great dance of the whole army corps, which, taken as a
whole, is the biont. The illustration is not quite exact, for
each company must not be considered as consisting of like
individuals, but of many individuals of all arms, some like
and some unlike, linked in such various ways that no two
companies are the same, partly because of the proportions of
different kinds of individuals composing them, partly because
of the way in which those individuals are linked together.
Nor must we imagine that individuals are permanently
attached to companies, nor yet companies to regiments, but
that in the course of the dance individuals are passed from
company to company, and companies from regiment to
regiment, each conforming temporarily to the particular
figure of that part of the dance to which he or it for the
time belongs. Further than this the individuals engaged
in the whole dance are never lone the same : there are
bystanders who for a time do not participate in the dance
but are caught up one by one, whirled through the figures,
passed from company to company, from regiment to regi-
ment and brigade to brigade, and are eventually passed out
of the dance again, after having participated in some or all
of the figures as the case may be. Every individual in the
dance is at some time passed out of the dance, becomes
a bystander, and may again be caught up and whirled along
in the dance once more.

The illustration is farfciful, if you please, but it is of the
same kind as illustrations used to depict the play of mole-
cular forces in the inorganic world. It serves a purpose in
that it gives the imagination something to work upon, and
it enables one to conceive of the immense complexity which
is possible in a chemico-physical process. The army dance
which I describe is capable of any number of combinations,
a number amply sufficient to satisfy the needs of those who
insist so strongly on the marvellous complexity of life.
Let anybody imagine an army to be composed of four
brigades, each brigade of four regiments, each regiment of
ten companies, and each company to contain 100 indi-
viduals of the eight kinds, carbon, oxygen, hydrogen,

THE PRESENT POSITION OF CELL-THEORY. 323

nitrogen, sulphur, phosphorus, potassium and iron, in
varying proportions, and let him work out the possible
combinations. I think he will be satisfied with the com-
plexity.

What then of heredity and of the capacity which I have
mentioned for acquiring historic qualities ?

Believing as I do that the vital processes must in the
end be attributed to a particular mode of molecular motion,
I believe that it is the form of movement which is trans-
mitted. Returning to my illustration I would say that it is
the figure of the whole dance which makes up the species,
and that it is the figure — the mode of motion — which is
inherited, clearly not the individuals engaged in the dance,
except in a very small degree, for they are constantly
coming into the dance anew and as constantly being passed
out of it. Under certain circumstances there may be an
excess of one or more kinds of new individuals pressing into
one part of the dance which will affect the figure of the
company dance which they crowd into, and this will affect
regimental figures and ultimately, in decreasing degrees,
the whole army figure. In this way we may picture to
ourselves the action of external influences in bringring about
variation. But I have given rein enough to my imagina-
tion. The picture was introduced partly to show that
beneath my obscure phrases there was some distinctness of
ideas, partly to emphasise the immense complexity of
Nature and to show that even atoms and molecules may be
conceived to be so combined together that, in Goethe's
words, " sie bewirken so eine unendliche Production aut
alle Weise und nach alien Seiten ".

Gilbert C. Bourne.

THE HEREDITARY TRANSMISSION OF
MICRO-ORGANISMS.

IT is well known that in the construction of many of the
theories of heredity the doctrine of the transmission of
acquired characters has obtained considerable prominence.
The hypothesis of Lamarck rendered it necessary to assume
that structural characters which had arisen from the use or
disuse of organs, became an integral part of the individual
and reappeared in the descendants, and although the appli-
cation of this idea became greatly restricted when the
principle of natural selection was established, it is only
within the last few years that the transmission of acquired
characters has been considered as unproven, and the in-
stances put forward in support of this view to be capable
of a different explanation. It may be admitted that mutila-
tions and permanent injuries can be included among acquired
characters, and the structural and functional modifications of
the individual which occur in disease may persist, and
therefore also be considered as definite morphological or
physiological changes. Mutilations apparently do not pass
from parent to offspring, and this has been especially pointed
out by Weismann and his followers, since, if heredity is
capable of explanation on the hypothesis of the continuity
of germ-plasm contained in definite reproductive cells, any
change in the structure or modes of activity of the essential
body or somatic cells would not be transmitted. An iden-
tical line of argument also negatives the belief that diseases
can be inherited, and this view was maintained by Weismann
in his well-known criticism on the transmission of experi-
mental epilepsy ; the symptoms in this hereditary disease he
considered might be due to some unknown microbe which
found its nutritive medium in the nervous tissues and
was transmitted in the reproductive cells. The question
whether micro-organisms can actually pass from parent to off-
spring is one which has been carefully investigated, whereas

TRANSMISSION OF MICRO-ORGANISMS. 325

the proof that actual morphological changes, such as modi-
fications of histological or molecular structure, can be trans-
mitted has not yet been given. It is conceivable that
predispositions may be inherited, and these must result
from alterations in the germ-plasm, or a direct infection of
the germ or embryo might cause the transference of a dis-
ease from one generation to another, a phenomenon which
simply depends upon a particular mode of conveyance of a
parasite.1

In many diseases, and particularly those which are directly
caused by micro-organisms, it is a matter of interest to note
the wide differences which exist between the conveyance
of hereditary characters, and of a specific disease. Armauer
Hansen (1) has made this perfectly clear in considering the
etiology of leprosy. He has pointed out that true heredi-
tary characters are usually limited to one sex, frequently
appear at a particular age, and the phenomenon of atavism
is not rare ; but in the conveyance of such a disease as
tuberculosis or leprosy, none of these conditions are ful-
filled. It is a logical deduction from the consideration of
these differences that every specific disease which is trans-
mitted cannot be regarded as hereditary, but as an instance
of the direct bacterial infection of the germ-cells or embryo.
Most writers on cancer and malignant growths have dis-
cussed the hereditary transmission of this disease, and if it
is allowed that a disposition to cancer may be derived by
inheritance, then this condition would depend upon some
peculiarity inherent in the nucleus of the germ-cells ; but
if, on the other hand, malignant disease is caused by a
parasite belonging, as some investigators have sought to
prove, to the group of protozoa or protophyta, then the
transmission of the actual disease will depend upon the
passage of a micro-organism which invades the germ or its

1 " Pour les maladies, vraiement constitutionnelles, c'est la substance
hereditaire elle-meme qui est viceuse; pour les maladies infectieuses, levice
n'est pas dans la substance elle-meme, mais a cote d'elle, et les produits
sexuels servent seulement de vehicule a un parasite capable d'engendrer
plus tard une maladie generate. " Y. Delage, La Structure du Protoplasma
et les Theories sur F Heredite. Paris, 1895.

326 SCIENCE PROGRESS.

product, and the whole phenomenon ceases to be one of
heredity, for the hereditary transmission of micro-organisms
is simply a particular instance of bacterial infection. The
inheritance of actual specific disease must therefore always
be considered as a problem absolutely distinct from that
of heredity and incapable of explanation by any hypothesis
of heredity.

Micro-organisms which reach an individual either by
inheritance or other modes of conveyance may undoubtedly
exhibit a period of latent life extending over many years ;
but when this condition is succeeded by an active life, to
establish the proof of an hereditary transmission is ex-
ceedingly difficult or even impossible (11). The early
researches into problems of this nature were necessarily
made with the help of statistical and clinical methods ; but
it is the application of experimental methods, which could
only be pursued with success as the study of bacteriology
developed, that has finally succeeded in removing the subject
of the hereditary transmission of specific diseases from the
hazy region of speculation. The attitude assumed by
Baumgarten and his followers on this question is well
known. In the case of tuberculosis it is maintained
that individuals are rarely infected with tubercle bacilli
after birth, but that the disease in the majority of cases is
due to a parasitic infection of the egg-cell or embryo. It
is even urged that the bacilli may remain latent in one
individual, and only enter upon a phase of activity in the
offspring, a view which, if correct, would accord with the
opinion of many clinical observers. While destroying the
opinion so commonly held that an "inherited tubercular
predisposition " exists, Baumgarten's theory of hereditary
parasitism makes a still greater demand on the imagina-
tion ; but that the views of this distinguished pathologist
have acted as a stimulus to renewed experimental work on
the transmission of micro-organisms is beyond doubt.
Recent papers by O. Lubarsch (2) of Rostock and J.
Csokor (3) of Vienna give an admirable exposition of the
present position of our knowledge on this subject of the
transference of bacteria from parent to offspring in man and

TRANSMISSION OF MICRO-ORGANISMS. 327

the lower animals, and the evidence that bacteria may in
this manner gain access to the organism is incontestable.

In inherited specific diseases it is possible to distinguish
two forms of infection : first, by a direct bacterial invasion of
the essential reproductive cells ; secondly, the egg-cell or
the embryo may receive micro-organisms from the female,
in which case the blood stream is the channel for conveyance,
and the whole phenomenon is then one of metastasis com-
parable in every respect to what obtains when bacteria
multiply at a definite area of the body, and thence become
distributed by the blood and lymph in distant parts of the
organism. Bacterial infection may therefore be either
germinative or placental, and in mammals the latter
form of transmission is not infrequently observed. The
specific bacteria of anthrax, typhoid fever (6), pneumonia
and tuberculosis (7) have been isolated from the human foetus,
cultivated, and successfully inoculated upon animals, so
that the chain of evidence is complete. The pyogenic
cocci such as streptococcus pyogenes (24) and staphylococcus
pyogenes aureus have also been demonstrated in foetal
tissues by Fraenkel and Kiderlen, and Auche has shown
that in small-pox the placenta may be penetrated by these
micro-organisms. In the lower animals not only may the
bacteria already mentioned be transmitted, but also those of
cholera, glanders and chicken cholera.

In many animals the egg-cell is the largest unit of the
organism, and would be capable of containing numberless
bacteria ; that such an infection does occur was first estab-
lished by the classical observations of Pasteur (4), which
have been confirmed by all subsequent investigators. In
pebrine, a disease of silk-worms, definite sporocyst forms
(microsporidia or Cornalia's corpuscles) are transmitted from
the imago in the egg-cell, and the larva is directly infected
in this manner. Blochmann (5) has also described a similar
mode of conveyance of bacteria in the ova of Blatta
orientalis. In a single instance a tubercle bacillus has
been seen in the mammalian ovum. The sperm-mother-
cells may also be invaded by micro-organisms, but this is
rare, and no example of an infected male reproductive cell

328 SCIENCE PROGRESS.

exists. That this condition will ever be demonstrated is
improbable, since bacteria contrast with parasitic protozoa
in infecting the cell and sparing the cell-nucleus, and the
essential agent in the process of fertilisation is the nucleus
or head of the sperm-cell.

Various observers have attempted a solution of this
question of germinative infection by the employment of
two different methods. The first of these is that pursued
by Mafifucci, who directly infected the fertilised eggs of the
fowl, and in the second not only were the genital glands
and the products of these examined for micro-organisms,
but pieces of them were taken from animals suffering with
specific diseases and used as material for inoculation.

Even if it is assumed that an ovum actually is a site in
which bacilli such as those of tuberculosis exist, it may be
objected either that the microbe is dead, or that such a cell
is incapable of development. This is the attitude taken by
Virchow, who absolutely denies the existence of congenital
tuberculosis. Maffucci's experiments, however, contra-
dict this opinion, for this observer has shown that the
bacilli of avian tuberculosis develop in an infected embryo,
and the chicken succumbs to tuberculosis in twenty days
to four and a half months after hatching. If, however,
instead of infecting the embryo, bacteria such as those of
chicken cholera, or anthrax, or Friedlander's pneumococcus
are introduced in the extra-embryonic area, then these
organisms may actually enter the embryo through the
allantois but do not increase in number provided the
embryo remains alive. The pathogenic micro-organisms
may therefore be destroyed or attenuated by actively pro-
liferating embryonic tissue cells, or they may become capable
of development at a later period of life, in other words,
remain latent. Although these experiments were devised
to establish the view that a genuine germinative infection
may occur, they obviously do nothing of the kind, and it is
to the researches of Gartner that we owe an absolute
demonstration that ova may contain pathogenic germs.
Gartner among: other animals inoculated canaries with mam-
malian tubercle bacilli. After a few weeks he removed

TRANSMISSION OF MICRO-ORGANISMS. 329

nine eggs, washed these in dilute corrosive sublimate,
dried them in wool and introduced the contents of each eo-or
into the peritoneal cavity of guinea-pigs. In two cases
tuberculosis was set up, the animals dying one and a half
months and two and a half months after infection. These
experiments, which are absolutely free from objection,
conclusively prove that the egg-cell may contain virulent
bacteria, and it is easily conceivable that such eggs may
develop and the transmission of the parasite take place by
direct germinative infection, especially since Maffucci's
work shows that such infected eggs are capable of develop-
ment.

Jani, Westermayer, Spano, Walther, Gartner, and quite
recently Jakh, have microscopically investigated the bac-
terial contents of the reproductive glands, and also inoculated
animals with fragments of these organs. With the exception
of Gartner's researches these experiments have not added
greatly to our knowledge of the hereditary transmission of
bacteria. All the experiments of Westermayer were nega-
tive. In fourteen cases of well-marked General tuberculosis
no tubercle bacilli could be recognised, and inoculation
experiments were failures. The experiments of Jakh (10)
were more fortunate. Five inoculations with pieces of the
male reproductive gland and its product, taken from in-
dividuals dead of tuberculosis, gave three positive results.
If the gland alone was used, the experiments were always
negative, and of three inoculations with pieces of the egg-
forming gland one was successful. It may be admitted that
these experiments do not really throw much light on the
subject of germinative infection, but Gartner's researches
are of much greater value. He experimented upon mice,
guinea-pigs, rabbits, and canaries, these birds being sus-
ceptible to mammalian tubercle bacilli. Having inoculated
these animals with bacillus tuberculosis, a careful examination
was made of the offspring of such tubercular parents. This
method might naturally be expected to give a conclusive
answer to the question of hereditary infection, and the
following information has been gained from these researches :
1. The sperm rarely contains tubercle bacilli — five in

23

330 SCIENCE PROGRESS.

thirty-two cases. Even if micro-organisms exist they are
incapable of infecting the egg. In twenty-two (rabbits)
and twenty-one cases (guinea-pigs) where the male repro-
ductive gland was the seat of an acute tubercular process,
the offspring were never infected. 2. Neither does the
male infect the female by way of the sperm. 3. Infection
takes place frequently from the female to the foetus, and in
an overwhelming majority of cases by way of the placenta.

A few considerations may make the importance of Gart-
ner's work more evident. If bacilli exist, as they occasionally
do, in the product of the male gland it is probable that this
material, like other parts of the body, contains bacteria only
a few days before death, for we know that quite an abnormal
number of micro-organisms may invade the whole organism
during the last days of life. Tubercle bacilli are immotile
and therefore will not easily reach the oviduct or egg, a
matter of some importance, since it has been shown that in
most cases the ovum is fertilised either high up in the
oviduct or even at the time of liberation from the Graafian
follicle. Stroganoff (12) has also pointed out that the
uterine area is sterile, and the secretion of this is bacteri-
cidal, in which it resembles sputum (13) or the mucus of the
nasal tract which is almost free from germs (14). Lastly, it is
well known that a single male morphological unit is sufficient
for fertilisation, and if we assume with Gartner that 100
virulent tubercle bacilli are mixed with sperm-cells, the
ratio of bacteria to these would be about 1 : 22,500,000 ; it
is hardly conceivable on the doctrine of probabilities that a
bacillus would gain access to the egg. It may therefore be
considered, both on experimental and theoretical grounds,
that a germinative infection of the ovum never occurs by
the conveyance of micro-organisms in the male reproductive
cells.

The difficulties which exist in proving that the in-
heritance of a specific disease may occur through an in-
fection of the ovum are fortunately not so great in those cases
where the passage of micro-organisms takes place solely
from the female to the fcetus by way of the placenta. It is
established that specific micro-organisms can pass by this

TRANSMISSION OF MICRO-ORGANISMS. 331

route. It is not even necessary to assume that there is any
lesion whatever in the placenta or that the epithelium of
the foetal villi is destroyed. An experiment by Zuntz
shows clearly that particulate material will easily pass into
the amniotic fluid from the maternal portion of the
placenta, for if indigo-carmine is injected into the veins
of the female the dye passes into the amnion leaving the
foetus free, and in this very manner anthrax bacilli may
pass, and from the amnion gain access to the mouth of
the foetus, enter the gut and set up disease by a
primary infection of the wall of the intestine (25). An intra-
uterine infection, therefore, can occur without lesion of the
placenta, though in the majority of cases this structure is
primarily infected, and then the foetus, or else haemorrhages
of the placenta permit the passage of micro-organisms.
However the undoubted fact that micro-organisms can

o

penetrate the healthy skin by way of the hair follicles — and
the same is possibly true for the epithelium of the urinary
tract — must not be forgotten in considering the passage of
bacteria across the placenta. This structure may be nor-
mal and even then allow the transit of bacteria. Birch-
Hirschfeld (15) from researches on the structure of the
human placenta as well as that of mice, rabbits and goats
considers that the bacilli of anthrax at any rate can
traverse the uninjured chorionic epithelium. Moreover in
the human placenta and in rabbits numerous processes of
the chorion traverse the placental sinuses, and these pro-
cesses are normally destitute of epithelium. It was noticed
by Max Wolff (16) that anthrax bacilli easily pass if the
placenta was crushed or torn, and micro-organisms which
exert a necrotic influence on tissues, such as the pyogenic
cocci, appear first to destroy the epithelium of the
chorionic villi, and then pass through into the foetal
blood. In this fluid micro-organisms reach the liver, and
it is this organ which, as a rule, is primarily affected, and
then the glands in the lymphatics leading from the organ
become implicated. The location, therefore, of tubercles
in foetal tuberculosis is characteristic, and all observers
insist upon this feature in determining whether tubercular

332 SCIENCE PROGRESS.

deposits are of intra- or extra-uterine origin in early cases
of the disease. As a matter of interest it may be
mentioned that quite recently Bar and Renon have de-
monstrated tubercle bacilli in the blood of the umbilical
vein (7). The method used by these observers, that of
inoculating guinea-pigs with the suspected blood, and in
this manner establishing tuberculosis, is not so convincing
as the actual demonstration of bacteria in fcetal tissues.
Wassermann (17) in a recent paper especially insists on
this point, and discards all evidence of inherited disease
which rests simply upon inoculation experiments. He
describes a case of early tuberculosis which ended fatally
when the child was ten weeks old, where the disease was
acquired, not from the parents who were healthy, but by
direct infection from a tubercular relation, and believes that
such cases as these are not infrequently cited as instances
of congenital disease. In his opinion hereditary trans-
mission of bacteria does occur, but it is exceedingly rare
in comparison with the frequency of extra-uterine infection.
Bernheim (18) considers that the offspring rarely, if ever,
become tubercular if separated from tubercular parents,
with the exception of those cases where the placenta is
infected. The case reported by Ivan Honl (19) of a child
fifteen days old that on autopsy showed tubercular nodules
in the liver, spleen, and lungs, and numerous bacilli,
must be classed as a definite case of transmission which with
many others lends no support to Eberth's statement that
individuals do not inherit tuberculosis but acquire it (23).

A recent case of congenital typhoid fever is related by
Freund and Levy (20), and instances of transmitted hemor-
rhagic infection have been recorded by Neumann (21) and
by Dungern (22). The numerous examples which the
journals of veterinary science contain, especially the work
of Bang, Kockel, and Lungwitz, also afford conclusive evi-
dence of the transmission of pathogenic micro-organisms,
though there is a consensus of opinion that the placental
is far more frequent than the germinative infection. The
share borne by the male in this transmission may be dis-
regarded, as no bacteriological evidence exists to support

TRANSMISSION OF MICRO-ORGANISMS. 333

this view. Finally, the frequency of hereditary transmission
of pathogenic germs is exceedingly small compared to other
modes of infection.

BIBLIOGRAPHY.

(1) HANSEN and LOOFT. Leprosy in its Clinical and Pathological

Aspects, 1895.

(2) Lubarsch. Ergebnisse der allgemeinen Atiologie der Mens-

chen-und Tierkrankheiten, by Lubarsch and Ostertag, p. 427,
1896. References to the transmission of infectious diseases
to descendants will be found in this and the following paper.
Some additional and later references are given in the course
of this article.

(3) Csokor. Ibid., p. 456.

(4) Pasteur. Etudes sur les maladies des vers a soie, t. i.,'p. 70,

1870.

(5) BLOCHMANN. Quoted by L. Pfeiffer in Die Protozoen als

Krankheitserreger ; 1 89 1 .

(6) Janiscewski. Munch, med. Wochenschrift, 1893.

(7) Bar and Renon. Comptes Rendus, No. 23, 1895.
Londe. Comptes Rendus, No. 25, 1895.

Nocard. Un nouveau cas de tuberculose congenitale. Rev.
de Tuberculose, No. 3, 1896.

(8) MAFFUCCI. Centralbl. f. Bakt. u. Parasitenkunde, Bd. v., No.

7 ; and Centralbl. f. allg. Pathologie, No. 1, 1894.

(9) Gartner. Zeitschrift f. Hygiene, Bd. xiii.

(10) Jakh. Virchow's Archiv, Bd. cxlii., 1895.

(11) Washbourne and others in the discussion on latent micro-

organisms at the Medico-Chirurgical Society, London.
Lancet, November, 1895.

(12) Stroganoff. Centralbl./. Gyndkologie, No. 38, 1895.

(13) Sanarelli. Centralbl. f Bakt., Bd. x., 1892.

(14) Hewlett. Lancet, June, 1895.

(15) Birch-Hirschfeld. Zieglers Beitr. z. path. Anat.u. allg.

Path., Bd. ix., 1891.

(16) Wolff. M. Intemat. Beitr. z. wissensch. Med. Festschr. f.

R. Virchow, Bd. iii., 1891.

(17) Wassermann. Zeitschrift f. Hygiene, Bd. xvii., 1894.
KOSSEL, H. Zeitschrift f. Hygiene, Bd. xxi., 1895.

(18) Bernheim. Erblichkeit und Ansteckung der Tuberculose.

Mitteilungen aus dem xi. internat. med. Kongresse in Rom,
1894. Reference in Centralbl. f Bakt., No. 17, 1894.

334 SCIENCE PROGRESS.

(19) Honl. Uber kongenitale Tuberkulose. Reference in Centralbl.

f. Bakt., Bd. xviii., 1895.

(20) FREUNDand Levy. Berliner klin. Wochenschrift,No. 25, 1895.

(21) Neumann. Archiv f. Kinderheilkunde, Bd. xiii.

(22) DUNGERN. Centralbl. f. Bakt., Bd. xiv., 1893.

(23) Eberth. Die Tuberculose, ihre Verbreitung und Verhiitung,

1 891.

(24) RlCKER. Centralbl. f. allg. Path. v. path. Anat., Jan., 1895.

(25) KOCKEL and LUNGWITZ. Beitr. z. path. Anat. v. allgem.

Path., Bd. xxi.

George A. Buckmaster.

Science progress*

No. 29. July, 1896. Vol. V.

PREHISTORIC MAN IN THE EASTERN
MEDITERRANEAN.

THE purpose of these notes is to summarise the results
of recent research among the prehistoric peoples and
civilisation of the Eastern Mediterranean ; especially in so
far as these prepare the environment for the first great
civilisation of Europe, namely, that of Greece, and fill the
chronological gap, and explain such communication as
existed, between this and the equally " historic " but far
earlier civilisations of the Euphrates and Nile Valleys.

A strictly " Historic " Age on the shores of the ^gean
Sea, or in fact in the Eastern Mediterranean at all, cannot
be said to begin before the seventh or at earliest the end of
the eighth century B.C. ; and everything before this point
would certainly have been classed as " Prehistoric," but for
the fact that, until quite lately, the preceding centuries have
been interpreted wholly in the light of a voluminous Greek
tradition, which is still accepted in many quarters as
fundamentally historical ; though now with wide reserva-
tions everywhere. Consequently prehistoric archaeology
and ethnology have here come into existence as accessory
and supplementary studies, and the data of the literary
tradition have been used, as was inevitable, as a working
hypothesis ; which, it is only fair to say, has served its purpose
fully as well as there was every reason to expect. Con-
sequently again, any account of the more recent and more

24

336 SCIENCE PROGRESS.

strictly anthropological work in this field must stand, if it is
to be intelligible, in close relation with the data and
assumptions, which have so mainly determined its course.

ANCIENT TRADITIONS AND MODERN INTERPRETATIONS.

i. The data upon which Greeks of the sixth and early
fifth centuries relied for the reconstruction of their own
history consisted wholly of traditional anecdotes, appended
to traditional genealogies, or grouped, in more or less organic
connection, round equally traditional events, such as an
invasion of the Troad, or an exploration of the Euxine, or
the adventures of a typical navigator like Odysseus. Many
of the lays in which these anecdotes were preserved can be
traced with some probability to their places of origin, which
range from Cyprus to the islands off the west coast of
Greece, and from Thessaly and the Troad to Crete. All
profess to represent the civilisation of the yEgean area at a
period removed by several centuries from the point at
which the Hellenic world emerges into history ; and the
traditional chronology of historical Hellas went up to an
era which is slightly later, but approximately contemporary
with the latest episodes of the Epic poems. Now though the
lays which display the greater literary skill and the maturer
idiom give a less vivid and more conventional picture ; and
though occasional allusions occur to customs and beliefs
which are characteristic of Hellenic culture, those others
which Greek tradition reckons primary, namely, the Iliad
and the Odyssey, are obviously at close quarters with their
subject ; and if there is one thing certain about the civilisa-
tion of the "Homeric Age" thus described, it is that it
differs in nearly every important feature from that of the
" Hellenic Age" of historical Greece.

2. The Greeks, in fact, themselves regarded their earliest
literature as antedating the chronological limits of their
history, and already perceived that they belonged to a
different order of things. In particular, the ethnography
of the /Egean, preserved in an admittedly late and de-
generate lay, differs uniformly from that of historic Hellas as
far back as it can be traced, and those names are almost

PREHISTORIC MAN, ETC. 337

absent by which the Greek race was denoted historically ;
by its western neighbours as "EAXiji'tc, by its eastern neigh-
bours as 'laoveg (Javan). This inconsistency was attributed
by the Greeks themselves to a period of invasion and
migration analogous to that which broke up the Graeco-
Roman civilisation of the Mediterranean. Dorian,
Thessalian and Boeotian mountaineers were represented as
forcing the barrier, or descending from the highlands, of the
Balkans, bringing the old established " Achaean " civilisa-
tion to an abrupt close, and reducing the /Egean, and
mainland Greece in particular, to a chaotic and barbarous
state, the recovery from which is the dawn of the historical
Hellenic genius.

3. Some facts within their own experience went to
confirm this view. Here and there tribes retained the names
and the mode of life of the earlier age ; or a noble family
professed to trace its descent beyond the limits of current
genealogy, and to identify itself with a Royal house of
Achaean princes ; and here and there ruined fortresses
remained, or ancient tombs had been disturbed, which
seemed to confirm the description of Achaean splendour in
the ballads.

4. Thus much had been established from the beginning
of Greek History onwards, and had not been seriously
shaken by successive attempts to discredit the traditional
view. The theories that the lays are comparatively late
compositions, and that they stand in no close relation to
a pre- Hellenic age ; that the Achaean Age is an invention,
and the Period of the Migrations a hypothesis to explain its
inconsistency with the facts of historical geography, all
prove too much, and may be met with argument a ad
hominem from the same traditional data. No literary
critic of the Epic has yet purged himself of a sediment of
traditional preconception ; and, in proportion as one or
another has attempted to do so, he has been reduced to a
merely agnostic position.

5. Further, until very recent years, every attempt which
was made to elucidate the civilisation of the Homeric Age
by the monuments of early Greek civilisation rested upon

338 SCIENCE PROGRESS.

the assumption that the representations of dress, armour,
etc., of the sixth, fifth and fourth centuries B.C., were valid
illustrations of poems which at the latest belonged to the
seventh, and on an average were assigned to the ninth or
tenth century. The reason of this was that Homeric sub-
jects in Greek art are uniformly furnished with accessories
of the age of the artist, and that until the study of Classical
Antiquities began to be infected with the " evolutionary
notions " which had already long been current in all other
departments of Ethnography, the attention of students of
Greek art and culture was strictly confined to mature and
decadent art ; everything which could not be assigned to a
century subsequent to the fifth was either dismissed as
barbaric, or discounted as a " Phoenician importation " ; the
part which " Phoenician " fables, ancient and modern, have
played in the historical study of the Mediterranean area will
be considered briefly later on. Such, for example, was the
received opinion — so far as there was one — of such dis-
coveries of pre-Hellenic culture as those of M. Fouque's
expedition to the Island of Santorin (Thera, 1862), where, in
the course of a geological investigation, a primitive settle-
ment was found under a thick bed of volcanic debris, or of
those of MM. Salzmann and Biliotti (1868-71), who in
searching for antiquities in Rhodes found at Ialysos, for the
British Museum, a magnificent collection of early vases
which are now known to be Mykenaean, and second only in
quality and variety to those from Mykense itself. The
Santorin settlement was simply taken to confirm the legend
of the Phoenician colony of Kadmos (Hdt. iv., 147), and
the vases from Ialysos were explained as the barbarous but
immediate predecessors of those from Kamiros, were classed
with them as " Grseco-Phcenician," and were referred to the
seventh century, in spite of the absence of Egyptian objects
of the twenty-sixth Dynasty, and the presence of objects of
the eighteenth : a view which in certain quarters is not
yet quite extinct.

6. It was not till 1871 that Dr. Heinrich Schliemann
was enabled to execute his lifelong ambition of testing with
the spade the Greek tradition that the site of the Grseco-

PREHISTORIC MAN, ETC. 339

Roman town of Ilion was also the site of Homer's Troy.
The tradition had indeed been sorely handled by Deme-
trios of Skepsis, a local antiquary of the second century
B.C., on the geological ground that the Plain of Troy is of
recent alluvial formation ; and by other critics on the score
of inconsistency with the Homeric narrative. But the Bali
Dagh, the site suggested by Demetrios, and in fact the
only alternative, is far more inconsistent, and is put
absolutely out of question by Dr. Schliemann's discoveries.
In successive seasons (1S71-3, 1876-82) he laid bare not
one, but six cities, built one after another on the same site,
and forming an accumulation of walls and debris some
thirty feet deep ; and, among these, two additional layers
have been distinguished in the confirmatory excavations of
Dr. Dorpfeld, 1892-94. The latter, however, indicate that
Dr. Schliemann's earlier work was not, from the circum-
stances of the case, sufficiently closely watched throughout,
and that in some cases objects were probably picked up at
lower levels than those to which they properly belong. In
particular, it is not clear that the cache of jewellery and
plate known as the "Great Treasure of Priam" was not
hidden originally in a shaft of some depth.

7. Dr. Schliemann claimed as the Homeric Troy the
Second Town from the bottom, which had perished by fire,
and in which the " Great Treasure " was found. But the
Sixth Town, which Dr. Schliemann described as Lydian,
was shown by Dr. Dorpfeld in 1892-93 to be larger and
more important than was at first supposed, and to cor-
respond closely with the remains found subsequently at
Mykenae and elsewhere.

8. With the same purpose in view of testing the
Homeric tradition, Dr. Schliemann proceeded in 1875-6 to
excavate the citadel of Mykenae, in the Peloponnese, the
traditional centre of the Achaian feudal confederacy. Here
the results were equally unexpected, but no less confirma-
tory of the legend. A civilisation was brought to light
wholly un- Hellenic, but far from barbarous ; greatly in
advance of all but the latest layers of Hissarlik, and
presenting already the marks of decadence after a protracted

34o SCIENCE PROGRESS.

career. The pottery, the personal ornaments, and in fact
the whole cycle of the art, were at once recognised as
identical with those of Ialysos, while the stone-fenced
burial-place discovered just within the " Lion Gate" of the
citadel, with its six " shaft graves " and their enormous
wealth of gold vessels and ornaments, seemed ample con-
firmation of the legendary wealth of " golden Mykenae,"
and was proclaimed, in the first enthusiasm of the discovery,
as the tomb of Agamemnon himself. The further re-
searches which have been made almost continuously from
1886 onwards by M. Tsountas for the Greek Archaeo-
logical Society have confirmed in all essential points the
first general impression, but the discovery of later tombs in
the lower quarters of the town has made it possible to trace
an order of progress and to extend the limits of the period.
9. Subsequent excavations at Tiryns and Orchomenos
by Dr. Schliemann, and on a number of other sites in
Greece and the yEgean Islands by the Greek Archaeo-
logical Society and the foreign Institutes in Athens, have
demonstrated that this civilisation, which has acquired the
provisional name of Mykenaean, is widely represented in
the yEgean area and especially in its southern part ; that
its influence extended over the Central and Eastern
Mediterranean from Sicily to Cyprus; that it penetrated,
intermittently at all events, into Egypt, where its appari-
tion can be approximately dated, and whence it imported
much, and borrowed somewhat, but without losing its own
individuality ; and, most striking of all, that, after a long
period of apparently continuous maturity, it falls into a
sudden decadence ; leaving, to all appearance, just the same
gap between itself and the first traces of Hellenic Art,
as we have noted already, on the literary side, between
the Homeric Age and the beginning of Hellenic His-
tory. It should be further noted, however, that in the
last few years many facts have come to light, especially in
Attica, in Crete, and, most of all, in Cyprus, which seem to
indicate how that gap may eventually be filled. It is from
the pottery, almost without exception, that the leading
indications have been derived. Fragments of baked clay

PREHISTORIC MAN, ETC. 341

are practically indestructible, even though the vessels which
they composed have been shattered. Moreover, all the
unrefined varieties of clay, and many even of the best
levigated, present features by which their place of origin
may be recognised. Consequently, in this material,
modelling and decoration can be perpetuated as in no other
way ; and, what is more important, the intrinsic worthless-
ness of earthenware has often preserved it from the dis-
placement and destruction which almost inevitably overtake
objects of gold, bronze, and marble. The resulting pre-
ponderance of ceramographic references in the bibliography
which follows these notes must therefore be taken as
indicating the character of the evidence which is most
accessible, and of the method which has actually proved
most fruitful : not that the pottery really took so large a
place in primitive art as might be inferred from its actual
abundance, and its scientific importance.

10. Consequently the study of Early Man in the JEgean
has entered within a few years on a new phase, and pre-
sents the following problems: (1) To reconstruct in detail
the history of the Mykenaean civilisation ; its origin, its charac-
ter, range and influence, and its decline ; (2) to investigate the
causes of that relapse into barbarism, which both literature
and archaeology attest ; (3) to determine the ethnological
position of the race, or races, who originated, maintained,
and overthrew it, and their relationship with the historic
inhabitants of the same area ; and (4) as a special study, to
determine the relation in which the Hellenic traditions of
the Achaean Age, and the lays in which they were preserved,
stand to the civilisation which they certainly seem to com-
memorate, and which owes its discovery simply to the
application to them of a new method of criticism.

(1) THE FIRST KNOWN CULTURE OF THE EASTERN

MEDITERRANEAN.

1 1. Palaeolithic Man seems to have left no traces in the
Levant comparable with those in North Europe, or with
the plateau and upper-gravel flints of the Nile Valley. But
the scarcity of evidence is partly due to the indifference of

342 SCIENCE PROGRESS.

the natives to such objects, and to the almost complete
diversion of trained research into more obvious and attrac-
tive departments ; partly also to the comparative rarity,
except in Egypt, both of workable flints and of the high-
level gravels in which they are usually preserved. From
Greece itself only one palaeolithic implement is recorded
hitherto ; a flint celt from Megalopolis in Arkadia (Rev.
Arch., xv., 1 6 ff).

12. Neolithic Man, however, can be traced over the
whole area. Masses of hard crystalline rock are frequent
and accessible, and furnished implements of characteristic
types ; short full-bodied celts, more or less markedly
conical behind, and ground to a rather obtuse edge. Ob-
sidian was largely exported from Melos and Thera to the
neighbouring islands, and to the mainland of Greece, and
was worked up at Korinth and on several sites in Attica.
Jade of good quality was sent from Asia Minor outwards
across the yEgean ; but it is not yet clear whether the
source of the common green variety is in Asia Minor itself
or further east : the jade implements become commoner
eastwards, and the finest collection from anysingle neighbour-
hood is that brought by Mr. D. G. Hogarth in 1894 from
Aintab in N. Syria (Ashm. Mus., Oxford).

13. Tombs of this stage of culture have not been found
— or sought — in sufficient numbers to justify discussion or
to contribute any facts of importance. The necropolis of
Psemmetismeno in Cyprus, for example, contains besides
typical early Bronze Age tombs a still more primitive class,
in which the pottery is exceedingly rude, and the charac-
teristic red-polished ware of the early Bronze Age is
wanting ; but though bronze is absent, no stone implements
are present. On the other hand the few tombs recorded
as containing stone implements are brought down by their
general character well within the Bronze Age.

14. Exception must however be made in favour of the
Nile Valley, for Professor Flinders Petrie in 1895 found,
at Ballas and Nagada, both tombs and villages of an
invading race, apparently Libyan, which had brought the
art of flint working to unequalled proficiency, and remained

PREHISTORIC MAN, ETC. 343

almost ignorant of the copper which was already in fairly-
common use under the Sixth Dynasty, which immediately
preceded their irruption into Egypt. But the significance
of this discovery and of our very limited knowledge of the
Libyan people and their civilisation will be better discussed
at a later stage.

15. On the other hand, several Settlements of the
Neolithic Age have been examined. Typical is the lowest
town of Hissarlik, though it has actually yielded a few
simple copper weapons. The implements are of local flint
and imported obsidian, of green-stone and allied rocks from
the interior of the Troad, and of jade ; some of the common
green Anatolian, others of finer yellowish kinds {cf. the
specimen in Ashm. Mus. attributed to Melos), and one
small celt of the pure white variety which is not known
to exist native except in China.

16. The fortifications and house walls of the "First City"
are of very rough unhewn rubble ; its pottery is of local
fabric, made wholly without the use of the potter's wheel,
and almost uniformly tinted black by a carbonaceous pig-
ment, intentionally applied and accentuated in the burning ;
many of the forms are closely allied to those of the neolithic
and early bronze ages in Central Europe, and of the corre-
sponding deposits of Greece and Cyprus. This lowest
settlement is separated from the rest by a layer of natural
soil, which represents an interval during which the site lay
desolate ; it is therefore distinctly older than the succeeding
cities. But the advanced and special technique of the
Pottery of the First City, and the fact that, on Schliemann's
authority, copper implements already occur, indicate the end
rather than the beginning of the Neolithic stage ; and the
Neolithic evidence from elsewhere is best summarised here,
before going further in the series at Hissarlik.

17. Settlements of similar character, but each with its
own local peculiarities, occur (r) on an unexcavated site,
commanding the Bosphorus as Hissarlik commands the
Dardanelles. (2) On the " Kastri " near Achmet-aga in
Eubcea, a low hill fortified with earthworks and approached
by a hollow way, like the hill camps of the south of England.

344 SCIENCE PROGRESS.

(3) Beside Dombrena near Thebes in Central Greece : the
site has not been described, but neolithic implements are
very frequent : among them is a potter's burnisher of white
quartzite (Finlay Coll., 280. Athens). (4) On the Acro-
polis of Athens many implements and vases were entirely
confused by the levelling of the summit in the fifth century
B.C. ; on the south side (in the space afterwards known as
the UtXapyiKov) is a layer of neolithic pottery with obsidian
flakes and a potter's burnisher, almost wholly destroyed
by the recent excavations, and only preserved where it is
left to support the fragmentary walls of the Mykenaean
settlement. The material of the pottery is Ilissos mud,
not the Kerameikos clay of the Kephissos valley. (5)
Beyond the Ilissos, between Hymettos and the sea, the
exact site is unknown, potsherds are common on the surface.
The many stone heaps in this district seem to have been
accumulated from off the fields on to barren spots ; two,
opened south-east of Kara in 1895, were quite barren; a
tumulus north-east of Kara, surreptitiously opened, con-
tained a Mykenaean interment (Ashm. Mus.). (6) Primitive
pottery is common on the west end of the cliff which runs
along the coast from New Corinth nearly to the site of
Lechaion.

18. The "Second City" of Hissarlik has marked points of
similarity with the first, but represents a decided advance,
and has notable characteristics of its own. The walls, great
and small, are of better masonry below, and of sun-dried
brick above, with bonding courses and terminal uprights
(antae) of timber ; the centre of the fortress is occupied by a
" chief's house," consisting of three oblong buildings with
portico entrances at one end in a courtyard entered by a
covered gateway. The pottery is still of unlevigated clay,
and mostly hand-made ; it is no longer blackened as before,
but either left as it is, or covered with a red slip, which con-
tinues to occur in the layers above ; new and characteristic
forms appear, some peculiar, others again common to
Central Europe, to the Greek islands or to Cyprus.
Stone implements are still in common use, but copper and
bronze begin to be frequent though they are still of simple

PREHISTORIC MAN, ETC. 345

types. But the pre-eminent feature of the Second Town is
the discovery of more than one buried " Treasure " of gold
and silver jewellery and vessels, the latter certainly of
local manufacture, for the forms closely correspond with
characteristic types of the pottery.

19. The Second Town perished in a general conflagra-
tion, and the Third, Fourth and Fifth Towns above it
never attained to anything like its magnificence. They
mark, however, a gradual advance of civilisation and form a
transition, more and more rapid as it proceeds, towards the
Sixth Town, a quite distinct and well-marked settlement of
" Mykenaean " invaders, in which imported pottery, and
native imitations of this, occur alongside of fully developed
indigenous forms, which again recall in characteristic details
many Central European types. This Sixth Town is the
only one which can be even approximately dated chrono-
logically ; it is certainly prior to 1000 B.C., and need not be
later than 1 300 ; the Fifth and lower settlements must of
course necessarily be older than this.

20. It has been already hinted that the " Treasure of
Priam " may belong to a period somewhat later than the
Second Town, though not so late as the sixth or
" Mykenaean " Town. Whether this be so or not, we
have in the jewellery an early example, perhaps a prototype,
of the characteristic gold work of the Mykenaean Age ;
but if the " Treasure " is contemporary with the layer in
which it was found, the time limit for the whole series at
Hissarlik must probably be contracted downwards. In
any case we must believe that the earliest civilisation of
Hissarlik was not so wholly barbarous as appears at first
sight.

21. Imported objects found at Hissarlik indicate a wide
range of foreign connections. The fragments of porcelain
point to Egypt ; the lapis lazuli axe from a neighbouring
site, to Turkestan ; the silver vases probably to the eastern
half of Asia Minor ; the types of the bronze implements
alike to Cyprus and to the Danube Valley ; and the amber
to the shores of the Baltic. This wide commerce does not,
of course, imply direct intercourse, but, from its geographical

346 SCIENCE PROGRESS.

position on the Hellespont, Hissarlik must have been a
point of convergence for any trade between the East and
Europe, and the catalogue of the allies of the Trojans in Iliad
II., though it refers to a later period, ranges them (i) up
the Hebros Valley into the Balkans, and along (2) the
North and (3) the West coast of Asia Minor; i.e., along
three well-known routes of early trade.

22. The metallic objects of Hissarlik are of particular
value as links between two principal copper-working areas,
Cyprus and Central Europe. The latter really falls
beyond our present view, but must be noted — mainly to be
rejected — as a possible source of the early Mediterranean
Bronze.

23. The use of copper in Cyprus goes back far beyond
the point where it can be dated with any certainty, and
everything goes to show that, while southwards, namely,
in Egypt under the Fourth Dynasty, Cypriote types appear
from the first side by side with others which are
probably Sinaitic, northward the same types extend, past
Hissarlik, into the Danube Valley, and are imitated and
amplified into derivative forms throughout Central Europe ;
returning, almost unrecognisable, into the Mediterranean
area in the series from Spain, which is clearly not directly
derivative, and may be of comparatively late origin.

24. The obvious suggestion that Central Europe may
have worked copper independently is met (1) by the com-
parison of the secondary forms, — e.g., only in Cyprus can the
actual synthesis of double-bladed axe heads, by welding
two simple ones, be observed ; (2) by the fact that, along
with the characteristic and indigenous metallurgy, the
ceramic technique of Cyprus, with red hand-polished sur-
face and incised ornament filled with white earth, can be
traced across Asia Minor and into South-eastern Europe ;
the red slip as far as Brus in Transylvania ; the ornament
into the Mondsee of Lower Austria, and the pile-dwellings
of Switzerland, becoming ever more mongrel and degenerate
as it proceeds.

25. It is important to note that at Hissarlik a return
current is already evident ; the pottery and the metal im-

PREHISTORIC MAN, ETC. 347

plements reproduce European types as well as Cypriote,
and this is confirmed, not only by traditional and
ethnological considerations, but also by the occurrence,
somewhat later, in the yEgean area, not only of frequent
amber, but of characteristically Danubian types of bronze
implements.

26. The Bronze Age civilisation of Cyprus is, thanks to
repeated researches, far more continuously and completely
known than any other part of the area. It was undoubtedly
of very long duration, and certainly follows that of the
Stone Age without change or break ; and it is no exaggera-
tion to say that, until a period between the twelfth and the
eighteenth Egyptian Dynasty, Cyprus was in all essential
respects in advance, not only of the coasts of Asia Minor
and the /Egean, but even of the coast of Syria and
Palestine.

27. All the earliest weapons, whether in Cyprus or
elsewhere, in Egypt, or the Levant, are of almost pure
copper. Tempering is effected, not by alloying with zinc or
tin, or, as in the Caucasus, with antimony from the natural
double-sulphide ore, but by " under-poling " the copper so
as to leave it hard and even brittle from the presence of
copper oxide. The same applies to the Egyptian copper
weapons of the fourth, fifth, and even sixth Dynasty ; but
Egypt, though later on it has important connections with
Cyprus, obtained its first copper from the mines of Sinai,
and has a set of typical forms peculiar to itself. Cyprus,
however, supplied the Syrian coast with copper weapons
down at all events to the time of the eighteenth Dynasty.
Stone implements are very rarely found in Cyprus,
and it is possible that either the island was not reached
much before the beginning of the Bronze Age, or that its
wealth of copper was discovered at once, and superseded
the stone age prematurely. In its earlier stages metallic
implements are rare, and the pottery — always made by
hand — is covered with a bright red glaze which was polished
with a stone or bone rubber (horse teeth were commonly
used), and ornamented, if at all, either by incised lines or
by pellets of clay rudely modelled after plants, snakes and

348 SCIENCE PROGRESS.

horned animals. In its earlier part, therefore, the civilisa-
tion, so far as it is known, is peculiarly uniform in character,
and displays no trace of foreign influence ; except only that
the characteristic red-polished glaze of the pottery, already
mentioned, is almost identical with that of the Neolithic
Libyan people of Ballas-Nagada, and of their " Amorite "
kinsfolk in South Palestine. Even here, however, there is
no evidence at present of imitation on either side. The
strong influence which Cyprus exercised, through its copper
trade, over the neighbouring coastland is best illustrated
by the discoveries of Dr. Bliss at Tell-el-Hesy, on the
coast plain of Palestine (Philistia), some sixteen miles from
Gaza. The site consists of an acropolis with eight "Cities "
superimposed as at Hissarlik. The mass of the remains
represent an indigenous "Amorite" civilisation of low type,
related, according to Professor Flinders Petrie, to that
of the Libyan invaders of Ballas-Nagada. But bronze appears
from the bottom of the series upwards, and iron already in
City Four, which with City Three appears to be contemporary
with the eighteenth Dynasty and the Mykenaean Age.
The bronze types are derivative, partly from Cyprus, partly
from Egypt ; and Cypriote importations of the later painted
fabrics occur in Cities Two and Three together with native
imitations. The red-polished pot fabric of Tell-el-Hesy,
however, belongs to the Amorite civilisation, and is not
necessarily borrowed from that of Cyprus.

28. In the latter half of the Bronze Age, Cyprus with
characteristic conservatism fell for a while slightly behind
its neighbours, and began to import ornaments and articles
of luxury from Egypt and the Syrian and Cilician coasts.
In this stage the red-polished ware tends to deteriorate in
colour and finish ; the bronze weapons become more
numerous, and contain a higher percentage of tin, and
occasionally jewellery of coarse silver-lead, all of native make,
is found in the more richly furnished tombs. Babylonian
cylinders occur rarely as imports, with a multitude of charac-
teristic native cylinders. Egyptian scarabs and porcelain
beads are also found rarely ; and with these again a very
common variety of coarse crumbly porcelain badly glazed

PREHISTORIC MAN, ETC. 349

with a very faint blue : the pigment was evidently difficult to
obtain, and was used but sparingly by the native artist.
But meanwhile the discovery of the art of ornamenting the
natural surface of clay vessels with an encaustic umber pig-
ment, wherever it may have originated, seems to appear
in Cyprus (where umber is extensively worked) at least
as early as anywhere else ; first in company with, but later
almost wholly superseding, the older mode of incising linear
ornaments on a prepared and polished surface.

29. The simply painted pottery is followed, though not
immediately, by several other fabrics which, though probably
native to Cyprus, are represented in some quantity on
Egyptian sites of the twelfth Dynasty and later dates, and
also in equivalent layers in the stratified mound of Tell-el-
Hesy, in the "Hittite" Sinjirli, and sporadically else-
where ; one very characteristic variety, with dark body,
white chalky slip, and black almost glossy paint, has been
found even so far afield as the Island of Thera, the Acro-
polis of Athens, and the " Sixth City" of Hissarlik.

30. The specimen from Thera was found in company
with vases of a distinct and local style ; some still with
coloured surface and incised ornament, others with simple
painted patterns. The forms, however, and the whole
fabric, are quite distinct from those of Cyprus, and show a
graceful freedom which is quite new; though they are clearly
derivative from a ceramic of the Hissarlik type. Most
important of all, the wholly geometrical and mainly linear
ornament which has been hitherto universal is combined
with or replaced by a thoroughly and vigorously natural-
istic study of animal and vegetable forms, and, in combina-
tion with the latter, spiral motives appear, hitherto unknown
but destined to a long and eventful career. These naturalistic
and curvilineardesigns are notonlyrepresentedon the pottery,
but are also frescoed upon the plastered walls of the houses ;
they may consequently be taken to be locally characteristic.
The settlement at Thera was found beneath a thick bed of
volcanic debris, and had evidently been suddenly abandoned ;
metallic objects are rare, but this may well be due, as M.
Tsountas suggests, to the flight of the inhabitants — for no

350 SCIENCE PROGRESS.

skeletons were found ; and a few copper implements and
gold ornaments remained to confirm the inference from the
pottery as to its position in the series.

31. Settlements and tombs of the same character have
since been noted in many islands of the Archipelago, especi-
ally in Syros, Melos, Antiparos and Amorgos ; and this
" Cycladic " type of ornament and general civilisation is not
only closely paralleled by the earliest remains at Mykense,
Tiryns, Athens and elsewhere, but is connected by an
almost continuous series with the fully developed art and
civilisation of the Mykensean Age itself.

32. It should be noted that though Cyprus appears to
have exported its own manufactures to the yEgean during
this period, it was not in a position to influence or direct
the Cycladic culture. But still less is there any trace that
the younger and more vivacious school reacted at all upon
the elder ; this was reserved for the full-grown culture of
Mykense.

2,7,. It is at this period that the Cretan evidence, though
as yet miserably incomplete, becomes of crucial importance.
Crete shares, to begin with, the early bronze age civilisa-
tion of Hissarlik and Cyprus, resembling the latter more
closely ; but it is not till the Cycladic stage is reached that
we have more than the most fragmentary evidence. In the
Cycladic period and in the succeeding age Crete was almost
literally tKaro^woXiQ, the " island of an hundred cities," and
certainly exercised a vigorous and continuous, perhaps even
a predominant influence upon /Egean civilisation. At this
point the wealth and variety of Cretan decorative art become
conspicuous, and a chronological point of the very first im-
portance and a clue to the origin of some characteristic
motives are given by the recent demonstration of a frequent
and fertile intercourse with Egypt in the time of the twelfth
Dynasty. On the one hand, a very peculiar and local fabric
of pottery from Kamarais in Crete has been found in twelfth
Dynasty layers at Kahun ; on the other, the Cretan types
of bronze implements are typically Egyptian, and twelfth
Dynasty scarabs were not only frequently imported, but
commonly imitated. In fact it is very probably from this

PREHISTORIC MAN, ETC. 351

quarter that the spiral motives, which are dominant in the
Egyptian Art of the twelfth Dynasty, were introduced into
the decorative repertory of /Egean art.

34. The seal-stones engraved with Egyptian and deriva-
tive spirals are closely associated in Crete with others
bearing groups of symbols, more than eighty of which have
been recorded, and shown to be hieroglyphic, by Mr. A. J.
Evans. They exist in two series, of which the earlier is fully
pictorial and naturalistic, the later conventionally abbre-
viated into linear forms. Some of the former are closely
analogous to certain Egyptian, others to certain " Hittite "
hieroglyphs from Kappadokian monuments ; many of
the latter are identical with graffiti on twelfth-eighteenth
Dynasty pottery from Kahun, Tell-el-Hesy and elsewhere,
and some are probably prototypes of symbols which per-
sisted in the Phoenician, Greek and Lykian alphabets, and
in the Cypriote syllabary. This hieroglyphic system is not
confined to Crete, though it is far best represented there
as yet ; the pictorial seal-stones are distributed over the
Cycladic area ; and two inscriptions in the linear character
have been found on vases at Mykenae. Dr. Kluge, of
Magdeburg, believes that he can translate these hiero-
glyphic inscriptions into a dialect of Greek.

35. We now come to what is, even literally, the Golden
Age of the early Mediterranean cycle. " Mykensean " Art
is still best and most completely illustrated by the long
series of discoveries in the plain of Argos, which at once
revealed its existence, and have given to it a name. The
monuments and the civilisation of Mykenae and Tiryns
have been repeatedly, though never yet really adequately,
described, and have given rise to the most divergent
theories as to their date, their origin, and their relations
with what precedes and follows them. The following
points are those which are chiefly made clear by the most
recent researches.

36. The limits within which Mykensean sites are dis-
tributed may now be defined with some approach to
accuracy, and no less the wider area over which Mykenaean
civilisation had a living influence. With the exception of

25

352 SCIENCE PROGRESS.

the "Sixth City" of Hissarlik no Mykenaean settlement is
known on the mainland of Asia Minor. Isolated vases are
reported from Pitane in JEoYis, from Mylasa in Karia, and
from Telmessos in Lykia, and the early necropolis of
Termera (Assarlik) near Halikarnassos (Budrum), though
of distinctly indigenous character, is strongly influenced, at
the very end of the period, by late Mykenaean models from
the neighbouring islands. Among the latter, besides the
great settlement at Ialysos in Rhodes, every island appears
to be represented from Rhodes southwards to Crete, and
northwards as far as Patmos. Both in Melos and in Thera
Mykenaean settlements are found distinctly superimposed
on the Cycladic already mentioned, and others are indicated
by isolated finds throughout the Archipelago. On the
mainland of Greece, Lakonia is represented by two sites
Kampos and Vaphio (Amyhlae), the latter with a princely
"beehive tomb" like those of Mykenae ; Argolis by
Mykense, the Heraion temple-site, Tiryns, Nauplia,
Trcezen, Epidauros, and the islands Kalauria and ^gina ;
Attica by Athens, Eleusis, Acharnae (Menidi), Aliki, Kara,
Spata, and Thorikos ; the rest of Central Greece by
Megara, Antikyra, Thebes, Tanagra, Levadia, Orchomenos
and several smaller sites in the Kopais marshes; North
Greece by Pagasae (Dimini near Volo) in Thessaly.

$*]. In the West there are no Mykensean settlements
known further than Kephallenia and Ithaka; but Mykensean
vases occur in domed rock tombs at Syracuse, and there is
much indirect evidence of Mykenaean influence on the later
Bronze Age style in Sicily and South Italy. Further than
this, it is clear that on the Adriatic coast of Italy Mykenaean
imports and models determined the character of the later
Bronze Age, and that in the transition from Bronze to
Iron at Hallstatt in the Tyrol, a definitely Mykenaean strain
can be detected. But in both these cases the contact is
with later and already quite decadent types, such as are re-
presented in the Lower Town of Mykenae ; in particular
fibulae are always present, and of these the secondary and
distinctly Sub-Mykenaean types are only very rarely absent.

38. Eastwards, Mykensean imports are found frequently

PREHISTORIC MAN, ETC. 353

in Cyprus, in the latest class of Bronze Age tombs,
and give a very distinct character to the necropoleis
of Episkopi (Kurion), Enkomi (Salamis), Pyla, Niko-
lidhes, and Laksha-tu-Riu. Native imitations increase in
frequency, and eventually supersede the importations and
fix the leading features of the art of the early Iron
Age, e.g., at Kuklia (Paphos), Lapathos and Katydata-
Linu. In Egypt again, Mykenaean importations are found
in great quantity, associated with the later Cypriote fabrics
and stimulating copious native imitation in layers of the
eighteenth Dynasty at Illahun, Gurob, Tell-el-Amarna.
These last finds confirm the date already inferred from
the occurrence of eighteenth Dynasty scarabs and porcelain
ornaments at Ialysos and at Mykenae, and fix the general
chronology of the Mykenaean Age beyond all question. The
contrary opinion, that the Mykenaean civilisation immediately
precedes the Orientalising culture of the seventh-sixth
centuries, and consequently itself descends as late as the
eighth-seventh centuries, has been vigorously urged by a
few English students, but has long been abandoned by all
who have had first-hand experience of the conditions of
discovery. The premature contention that the fortress of
Tiryns was Byzantine deserves mention, but is obsolete.

39. It is in Egypt also, moreover, that the first notice
occurs of the actual peoples who transmitted the civilisation
in question, and this in a peculiarly suggestive connection.
In the fifth year of Merenptah (1225) and under Rameses
III. (1 1 80- 1 150) the western frontier of Egypt was seriously
threatened by a Mediterranean coalition, of which the
Libyans were the principal members, but which included
under the general description of " the peoples of the isles
of the sea " a number of tribes whose names, though much
distorted in the Egyptian hieroglyphic records, strongly
resemble those of Achaians, Danaans, Ionians, Teucrians,
Tuscans or Tyrrhenians, and perhaps Sicilians and
Sardinians. Neither these names, of course, nor yet the
apparent resemblance of their arms and furniture, as depicted
in Egyptian paintings, can give more than a plausible pre-
sumption of identity either with historical /Egean races or

354 SCIENCE PROGRESS.

with the representatives of Mykenaean civilisation. But the
analogies are on all sides so close, that the identification is
usually accepted, and that as soon as even the outlines of
the history and civilisation of Libya during the Bronze Age
are ascertained, we shall be in a position to formulate
the real relations which then existed between Libya
and the /Egean, and probably also to trace more clearly to
its source the very remarkable realistic instinct which dis-
tinguishes the art of the y^Egean from all contemporary
styles.

40. The sudden collapse of the Mykensean civilisation,
which was indicated to begin with, is roughly coincident with
the first appearance of Iron in common use in the Levant, and
the attempt has been made, though on no direct evidence,
to connect the two tendencies. All the facts go to indicate
that, so far as the Mediterranean area is concerned at all
events, iron makes its appearance first on the Syrian coast,
in the period which immediately succeeds the downfall of
Egyptian suzerainty in that area under the nineteenth and
twentieth Dynasties: e.g., at Tell-el-Hesy iron occurs down to
the fourth "City" (= eighteenth Dynasty). The ambiguity
of the Egyptian allusions under the eighteenth and previous
Dynasties makes any earlier date uncertain, and iron has
not been actually found in Egypt before the twenty-sixth
Dynasty, 650 B.C. In Cyprus, where the evidence is com-
pletest, and where abundant native ores have certainly been
worked from an early period, iron suddenly becomes very
common just at the point when Mykensean vases are ceasing
to be imported, but when, on the other hand, Mykenaean
conventions have already begun to influence profoundly the
native scheme of ornament. At Mykenae itself iron occurs
first as a " precious metal " and in the form of signet rings, at
the stage where decadence begins to be rapid, but it is not
put to practical uses till the moment where the series breaks
off, and the same is the case in other Mykenaean sites in
the iEgean ; one iron sword was found in the Vaphio " bee-
hive ".

41. Up the Adriatic again it is with the early fibulae and
quite degenerate Mykenaean art, that iron makes its appear-

PREHISTORIC MAN, ETC. 355

ance, at Novilara ; and at Hallstadt ; and here again, both in
tradition and among the finds, there is evidence that the
metal became established first as an ornamental rarity, and
only subsequently as a substitute for bronze.

42. But though in its principal centres Mykensean
civilisation has all the appearance of having been suddenly
and violently extinguished, this must not be taken to be
universally the case. In Argolis (at Tiryns, and the Heraion),
in Attica, and in Melos, for example, there is every reason to
believe that the Mykenaean civilisation survives, though in
very degenerate phases, into the period when Iron and the
characteristic art of the early Iron Age are already well
established ; and at Nauplia and the Attic Salamis, and
still more in Crete, in Karia, and in Cyprus, the stages may
be clearly traced by which, so far as in it lay, the Iron Age
took up its inheritance from the Age of Bronze. The
nature and the result of this transference are easily sum-
marised.

43. It has been already indicated, firstly, that through-
out the Eastern Mediterranean, in fact throughout the whole
range of the Mediterranean Early Bronze Culture, the
indigenous system of decoration is instinctively rectilinear
and geometrical ; secondly, that in the Cycladic area and
in the Middle Bronze Age a quite irreconcilable and purely
naturalistic and quite heterogeneous impulse appears ; and
thirdly, that the fully formed Mykenaean style, when it
appears, is, in spite of its far superior technical skill and
elegance, already beginning to stagnate in many depart-
ments ; the gem-engraving and modelling developing last,
and retaining their vigour and elasticity latest ; whereas
the ceramic decoration, which appears in its noblest
form at Thera and at Kamarais, is the first to exhibit the
conventional and mechanical repetition of a shrinking
assortment of motives. We may now add, fourthly,
that this failure of originality permitted of a recrudescence
of the rectilinear instinct which, though overwhelmed for
the time by the naturalistic and curvilinear principles, had
co-existed with them throughout ; and that both floral and
spiral motives, once allowed to repeat themselves without

356 SCIENCE PROGRESS.

reference to their models, are transformed automatically
into the latticed triangles and maeanders, which are the
commonplaces of rectilinear design.

44. At this point the survey must close, for now, on
geometrically engraved tripods, and geometrically painted
vases, appear Hellenic inscriptions in alphabetic characters.
Borrowed Oriental, and especially Assyrianising, motives
intrude themselves into the panels of the rectilinear orna-
ment, and attempts are made, however ineffectual, to
represent first animal and then human forms. Now, in the
development upward out of the " Dark Age," Hellenic
history begins to reckon onward from the Trojan Era and
from Olympic and kindred lists ; and Hellenic art no longer
forward from the eighteenth, but backward from the twenty-
sixth Dynasty.

LEVANTINE ETHNOLOGY, AND SUMMARY (to follow).

BIBLIOGRAPHY.

N.B. The references which follow are grouped under
the numbers of the paragraphs of the text. They only
indicate the primary researches and theories, and must be
compared with the fairly full references in Perrot and
Chipiez, Histoire de I Art. VI, La Grece Prehistorique,
1895, and with the current notices of discoveries scattered
throughout M. Salomon Reinach's invaluable " Chroniques
d'Orient " published in the Revtie ArchcEologique, of which
the years 1883- 1890 have been republished separately
(Paris, Firmin Didot, 1891).

6. Dr. Schliemann's Researches.

Schliemann. Ilios. (German and Englished.), 1881, (French
ed., including " Troja"), 1885, (German and English), 1884.
Atlas Troj. A Iterthumer (photographs), 1874.
Mycence ,, ,, 1878.

Ithaka, etc., ,, ,, 1879.

OrcJwmenos ,, ,, 1881.

Tiryns ,, ,, 1886.

SCHUCHHARDT. ScJiliemanii s Excavations (German, Leipzig,
1890); E. T. Macmillan, 1891.

PREHISTORIC MAN, ETC. 357

11. The Stone Age. Sp. LAMBROS. 'Ia-opiKa MeXeryj/xara

{Historical Essays), ch. i.
Dumont. Materiaux pour servir a Fhistoire primitive de

rhomme, 1872 (Finlay Collection). Revue ArchcEologique, xv.,

pp. 16-19, 356 ff., xvi., p. 359 (1867).
PAPPADOPOULOS. AiQwi) kiroyy) ev rfj Mifcpa ' Aa'ia (Stone

Age in Asia Minor), Smyrna, 1875. Cf. Bulletin des

Correspondances Helleniques, ii., p. 8, 1876.
FlNLAY. UapaTtipriaei<i {Observations), Athens, 1869.

13. Psemmatismeno. DtJMMLER. Athenische Mittheilungen, xi.,

pp. 214-6, 1886.
Bronze Age Tombs with Neolithic Implements. At Kurion in
Cyprus. Archives des Missions, xvii., p. 6. Cypr. Museum
Catalogue, No. 470 (Oxford, 1 896). At Tiberiopolis in Phrygia.
J. A. R. Munro. Journ. Roy. Geog. Soc. (forthcoming).

14. Ballas-Nagada. Catalogue of Exhibits, University College,

London, July, 1895; Academy, 20th April, 16th July,
1895 (Report forthcoming).

15. Jade. SCHLIEMANN (Maskelyne). Ilios. (English), p. 240.
FISCHER. Neplirite u. Jadcite . . . uach Hirer Urgesch. u.

Ethnogr. Bedeutung, Stuttgart, 1875.
Davies. Geol. Mag., second decade, v., 4, April, 1878.

16. Hissarlik, v. § 6, SCHLIEMANN.

NORMAND. La Troie d'Homere (popular, well illustrated).

17. Thymbra. SCHLIEMANN. Ilios. s. v.

Boz-oyuk (Phrygia). Jahrbuch d. K. Akademie, Berlin, xi.,

1896. Anzeiger, p. 34.
Salonika. Jahrbuch, I.e.
Thessaly. Mitth. Ath., p. 99 ff., 1884.

18. Bceotia. Jahrbuch, 1895. Anzeiger, p. 32.

J.H.S., pp. 54-56, figs. 10-13, 1884.
Attica. Mitth. Ath., p. 138, fig. 31, 1S93.
Jahrbuch, p. 16, 1893.
22ff. MUCH. Die Kupferzeit in Europa (second edition), Jena, 1893.
Naue. Die Bronzezeit auf Cypern. Korresp. Blatt, p. 124, 1888.
VlRCHOW. Zeit. d. Deutsch. Gesellsch. d. Anthrop., xii., 73.

27. Copper and Early Bronze with but little Tin. J. H. GLADSTONE.

Proc. Brit. Ass. (Nottingham), p. 715, 1893. Trans. Soc.
Bibl. Archeology, xii., pp. 227-234. Flinders Petrie.
Zeitschr. f. Ethu., p. [477], 1891. BLISS, I.e.
Tell-el-Hesy. BLISS. A Mound of Many Cities, 1894.

28. Cyprus. Sandwith. Archcsologia, 1877.
DtJMMLER. Mitt. Ath., xi., 1886.
OHNEFALSCH-RlCHTER. Kypros the Bible and Homer, 1892.

358 SCIENCE PROGRESS.

Myres and OHNEFALSCH-RiCHTER. Cyprus Museum Catalogue,
Oxford. 1896 (in the press).

30. Thera. FOUQUE. Santorin. Archives des Missions, ser. 2,

vol. iv.

31. Cyclades. Dummler. Mitth. Ath., xi., 1886.
Antiparos. Bent. /. H. S., x., 1887.

33. Crete. A. J. Evans. Journ. Hellenic Studies, xiv., pp. 276-372,

1894 (republ. "Cretan Pictographs," etc., Quaritch, 1895).

34. y£gean Hieroglyphic System. Evans, I.e.
KLUGE. Magdeburger Zeitung, 1896.

35. Mykenaean Civilisation in general. v. Bibliogr. in PERROT,

vi., q.v.
TSOUNTAS. Mvxrjvai fcal Muk. ttoXlthtpos (Mykenae and

Myk. Civilisation), Athens, 1893.
TSOUNTAS. sE^>rffi€pU 'ApxaioXoyL/cr) {Journal of Gk. Arch.

Soc), 1 886- 1 894, passim.
PERROT and Chipiez. Histoire de I'Art, vi. (la Grece

Prehistorique) (E. T.), 1895.
FURTW/ENGLER u. LcESCHKE. Myk. TJiongefdsse, 1879.
FURTW^ENGLER U. LcESCHKE. Myk. Vasen, 1886.
POTTIER. Vases Antiques du Louvre, I., p. 181 ff., 1896.
HELBIG. La Question Myce'nienne. Paris, 1896.
^6. Mykenaean Sites, Asia Minor : —

Hissarlik, "VI." DCERPFELD. Troja, 1893. Mykenische
Vasen, p. n. Reinach. Rev. Arch., 1893, i., p. 357. Rev.

Arch., 1895, i., p. 1 13.
Pitane (zEolis). PERROT, vi., Fig. 489-91.
Lemnos. Rev. Arch., xxvii., 1895, Nov. -Dec. ; cf. Smyrna

Museum.
Telmessos. Mitth. Ath., xii., pp. 228-230.
Thessaly. WOLTERS. Mitth. Ath., xiii, p. 262, PI. viii.-xi., 1889.
Orchomenos and neighbourhood. SCHLIEMANN, q.v. De

Ridder. B. C. H., p. 137 ff., 1895. Esp. Gha. De Ridder.

B. C.Lf.,p. 271 ff., 1894. Noack. Mitth. Ath,, xix., 1894.
Daulis. {Athens: National Museum), unpublished.
Antikyra (Phokis). Lolling. Wolters' Mitth. Ath., xiii.,

p. 267, 1889 (identified with Medeon).
Athens. TSOUNTAS. *E<f>. 'Apx-, 1891, p. 27 ff.

GR/EF. Jahrbuch, 1892. Anzeiger, p. 16 ff.
Wide. 'Adtjvcuop, ii., 1895, 168.
Eleusis. Philios. 'Ecp. 'Apx-, 1889, p. 171.
Koropi. Bruckner. Mitth. Ath., xvi., p. 200 ff., 18

(identified with Pallene).
Sal am is. (Athens: National Museum.)

PREHISTORIC MAN, ETC. 359

/Egina. Evans. /. H. S., p. 195 ff., 1892-93 (Gold-find).

Reinach. Rev. Arch., November-December, 1895.
Kalaureia. Wide. Mitth. At//., xx., p. 297, 1895.
Troezen. Reinach. Chroniques, p. 628.

Epidauros. [Athens: National Museum.) 'Apx AeXrlov, 1888.
Kephallenia. Wolters. Mitth. Ath., xix., pp. 486-490.
Crete. Milchhcefer. Die Anfange d. Kunst, p. 122 ff.
Evans. /. H. S., xiii., pp. 276-372, 1894 (republ. "Cretan

Pictographs," Ouaritch, 1895).
FURTW.ENGLER u. LCESCHKE. Myk. Vaseil, pp. 22-4.
Halbherr and ORSI. Museo Italiano, II., p. 908, pi. xiii.-xiv.
Haussoullier. B. C. H., 1880, pp. 124-7.
Joubin. B. C. H., 1892, p. 295.
ORSI. Monumenti AnticJii d. Accad. d. Lincei, I., p. 201 ff.,

1890.
Perrot, vi., p. 451 ff. (bibliography).
Sicily. ORSI. Bulletino di Paletnologia Italiana, xviii., pp.

193 ff., 206 ff , xx., p. 257 ff. Necropoli Sieu/a, p. 30 ff.
Spain. GASCON de GOLOS. Saragoza, i., pi. iii., p. 40.
39. Chronology — For eighteenth Dynasty dates : —

Flinders Petrie. /. H. S., xii., pp. 199-205, 1891.
Perrot, vi., p. 1000 ff.
For later dates (summary) : —
REINACH. Chroniques, pp. 420, 575 ff Rev. Arch., p. 75, 1893.

Classical Review, p. 462 ff, 1892. Times, 6th January, 1896.

Academy, nth January, cf. 1st February, 1896.
Torr. Memphis and Mykence. 1896.
For " Byzantine " Tiryns (summary) : —

Reinach. Chroniques, p. 280 ff, V Anthropologic, p. 701, 1893.

J. L. Myres.

THE GRAPTOLITES.

THERE is, perhaps, no better illustration in geology of
the value of detailed work than that which is fur-
nished by the group of organisms, to the consideration of
which this article is devoted. Formerly viewed with sus-
picion by biologist and geologist alike, and frequently
altogether ignored, we find the graptolites now treated
with respect even by those who have not devoted special
attention to them. Their value is generally recognised as
aids in the determination of the age of strata, but besides
this, a detailed study of the group will undoubtedly throw
light upon the physical and climatic conditions under which
the strata containing graptolite remains were deposited, and
also upon the evolution of the various forms of graptolites.
Every one will admit that the appreciation in which grapto-
lites are now held is largely due to three papers by Professor
Lapworth, one of which treats of these organisms from a
biological (i), and the second (2) and third (3) from a
stratigraphical point of view ; and the publication of these
papers is doubtless largely responsible for the appearance
of a large number of memoirs devoted to a study of the
group under consideration which have been written of
recent years. These recent memoirs it is the object of
this paper to consider.

The memoirs, early and more recent, treating of the
graptolites are scattered through a variety of publications,
but an excellent bibliography compiled by Otto Herrmann
and published in his Inaugural Dissertation (4) gives a list
of these memoirs up to and including the year 1883. Even
with this guide the student has much difficulty in obtaining
access to some of the publications, and a general monograph
of the graptolites has yet to be written. In the list of
" Monographs which are promised or are in course of
publication " appended to the last " Monograph of the
Palaeontographical Society" we note "The Graptolites," by
Professor Lapworth, and all geologists must hope that ere

THE GRAPTOLITES. 361

long the professor will give to the world the full results of
his prolonged researches into the history of the group.
This monograph must necessarily be confined to an account
of the British graptolites, but when that is complete surely
Professor Lapworth will treat of those of other countries
also.

The graptolites, at one time referred by some writers to
the Hydrozoa, by others to the Polyzoa, are now generally
admitted to belong to the former class, though the exact
value of the sub-division is not definitely settled, for whereas
we find Professor von Zittel in his Paleontology treating of
them as a sub-order, Graptolithidse (= Rhabdophora, All-
man), divided into the groups Graptolitoidea Lapw. and
Retioloidea Lapw., Nicholson and Lydekker {Manual of
Paleontology) place them in a sub-class (Graptolitoidea).
In these works the general structure of the graptolites is
described, though, as will be seen in the sequel, one structure
supposed to be absolutely characteristic of all graptolites,
namely the virgula, is not really so. Comparatively little
has been added to the knowledge of the histology of the
graptolitoidea furnished by H. Richter (5), though some of
his results have been confirmed by Professor Sollas (6) ;
and additional information has been supplied by Professor
S. L. Tornquist (7) and Dr. Perner (8). Some of the most
important papers published of recent years treat especially
of the mode of growth of the proximal portions of the
graptolites. The first of these by Tornquist (9) is occupied
with a description of sections through several deprionidian
graptolites. The author distinguishes the obverse from the
reverse aspect of the polypary, and also introduces two
terms to distinguish its right and left portions — the " primor-
dial " portion, containing the "primordial" series of hydro-
thecae, is marked by the possession of the earliest hydro-
theca, whilst the other portion is termed the "second"
portion and possesses the second series of hydrothecse.
When the obverse aspect of the polypary is turned towards
the observer the primordial series of hydrothecae is in-
variably on the left hand. The sicula sends out what the
author terms a " connecting canal ' which opens into a

362 SCIENCE PROGRESS.

" biserial chamber," thus producing a connection between
the various parts of the polypary. These features are
common to all the forms described by the author, but the
forms differ in other respects. In Climacograptus scalaris
Linn, and Climacograptus internexus Tornq. the biserial
chamber communicates with two uniserial canals separated
from one another by a median septum. In Diptograptus
palmeus Barr. the septum scarcely extends through half the
thickness of the polypary, whilst in Cephalograptus cometa
Gein. it is " reduced to a narrow7 fold of the obverse peri-
derm," and in Diptograptus bellutus Tornq. it is altogether
absent.

Two papers by Wiman (10) treat of the structure of the
Diptograptidce and of Monograptus. Notices of these papers
by E. M. R. Wood and G. L. Elles appear in the Geological
Magazine for 1895, p. 431. The accounts of the structure
of the sicula, and of those parts of the polypary immediately
in contact with it, are largely confirmed by Holm in a paper
to be noticed immediately, but the statement that the Dip-
tograptida; are monoprionidian because the sicula gives rise
to only one bud (which is on the right hand side) involves
a special use of the term monoprionidian which will hardly
meet with general acceptance.

A most important paper by Gerhard Holm must now be
noticed (11). Holm has had the advantage of studying
some beautiful material derived from the J^aginatus-Yimestone
(of Areing age) from various localities in the northern part
of the Island of Oland ; the graptolites of this limestone he
has succeeded in freeing from the matrix, thus rendering
them serviceable for detailed study. (The method of re-
moving the matrix is described by Holm in an article in
Bihang K. Vetensk. Akad. HandL, Bd. xvi., 1890.) In the
present paper he gives reasons for supposing "that the
earlier development of the proximal part — the first three
thecae — in all the bilateral or diprionidian forms of graptolites
is in the main the same, and has taken place through the
formation of only one bud on one side of the sicula — -or first
theca, as I believe it is — which side is always the same in
relation to the later development of the polypary. From

THE GRAPTOLITES. 363

this bud thereafter is developed partly the second theca,
partly the canal — ' connecting canal ' — which connects both
halves of the polypary, and which in the first place gives
origin to the third theca (= first theca on opposite side of
sicula), and partly also the common canal which connects
the second theca with the succeeding ones." He describes
the " sicula " which consists of two distinct portions, the
"initial part" which he believes to correspond with the
original " chitinous covering of the free zooid germ or em-
bryo," and the apertural part which has the same function
as a theca and may therefore be justly considered as the
first theca. Accordingly Holm's second theca corresponds
to Tornquist's primordial one, and his third to Tornquist's
second.

The sicula in the bilateral graptolites does not occupy a
central position, being partly embraced on one side by the
connecting canal, whilst on the other side it is more or less
superficial. The sicula side is termed the "anterior," and
the other the "posterior". These are used in the same
sense as that in which Tornquist employs the terms "ob-
verse aspect" and "reverse aspect". The author gives a
full account of the connection between the sicula, the first
theca, the first bud, from which " arises almost simul-
taneously with the left theca the common canal for the
left half of the polypary, and the connecting canal which
crosses the dorsal side of the sicula and gives origin to the
third (or, better, the right) theca lying on the right side of
the polypary, and also the common canal for the right side
of the polypary," and describes the growth of these in
Didymograptus minutus Tornq., D. gracilis Tornq. mut., D.
gibberulus Nich., Tetrgraptus Bigsbyi Hall, and Phyllo-
graptus angustifo/ius Hall.

He maintains that a virgula cannot occur in any
graptolites of the families Dickograptida, Dictyogr apt idee,
and Nemagraptidce, or in the genus Dicellograptus of the
family Dic7'anogiraptid&. The true virgula commences
near the apex of the sicula as a prolongation of the same,
and corresponds with the thread-like prolongation of the
sicula which has long been known in Didymograptus

364 SCIENCE PROGRESS.

gibberulus, and certainly occurs in many other forms of
Dichograptidce. Another filiform appendage which might
be spoken of as the false virgula " originates as a result of
growth within the apertural end of the sicula at some
distance from the initial portion. This later structure
stands evidently in no relation whatever to the real
virgula, but may be regarded as an apertural spine." The
significance of these filiform processes has not yet been
fully explained, but the possession of a true virgula must in
future be omitted from diagnoses of the characters of the sub-
class or sub-order of the graptolites. Holm's researches
fully confirm Tullberg's inference that Phyllograptus belongs
to the family Dichograptidce, and the family Phyllograptidcz
must now be abandoned. Another interesting point bear-
ing upon classification is the position from which the bud
grows out of the sicula. " In Phyllograptiis it is situated
quite close to the apex of the sicula, in Tetragraptus
Bigs by i Hall probably slightly lower down, in Didymograptus
miniUus Tornq. somewhat below the middle of the
sicula, in Didymograptus gracilis Tornq. Mut. still nearer
the aperture ; but in Didymograptus gibberulus Nich. the
position is almost the same as in Pliyllograptus." The
reference of the genus Azygograptus to the Nemagraptidce
on account of the stipe being developed from the central
part of the sicula on one side is therefore unnecessary, and
the general characters of Azygograptus leave no doubt
that it belongs to the Dichograptidce ; indeed Holm in the
paper under consideration describes a form which is possibly
intermediate between Didymograptus and Azygograptus.

The association of a number of graptolites of the same
species in a fairly symmetrical manner has long been
known. James Hall in plate xiv. of his classic work on
graptolites (12) figures a diprionidian graptolite under the
name of Retiograptus teutaculatus, and in figure 9 is "an
illustration of a compound form of the genus," possessing
nearly twenty diprionidian stipes diverging from a common
centre. James Dairon (13) also figures specimens of
Monograptus occurring in partly symmetrical tufts, and
remarks : " I am now thoroughly convinced that many, if

THE GRAPTOLITES. 365

not all, of the specimens of Monograptus may have been
fixed to the sea-bottom, or to objects lying or growing on
it, and not have been free-floating organisms, as has hither-
to been supposed, until at last they were separated from
their points of attachment by breakage or some other
natural cause ". Recently a remarkable description has
appeared (14) giving an account of specimens of Dipto-
graptus pristis Hall and D. pristiniformis Hall from
the Utica Slates. In these specimens the stipes occur in
"compound colonial stocks which appear in the fossil state
in stellate groups ". From observations on the specimens,
the author infers "that the colonial stock was carried by a
large air-bladder, to the underside of which was attached
the funicle. The latter was enclosed in the central disc,
and this was surrounded by a verticil of vesicles, the
gonangia, which produced the siculae. Below the verticil
of gonangia and suspended from the funicle was the tuft
of stipes," the latter being so arranged that the " sicula-
bearing end of the single stipes appears in the compound
colonial stock as the distal one ". The paper is only an
abstract of one which is promised shortly, and geologists
will await with interest a full account of these remarkable
specimens. The structure described as a funicle can hardly
be looked upon as the analogue of the " organ" described
by Hall under that name (which by the way has been
proved by Brogger and Holm to be celluliferous in many
species, so that Holm is doubtless correct when he says
that a funicle has not been found in any graptolite). It
is remarkable that the author should explain what he
means by the assertion that the chitinous capsule which
encloses the " funicle ': on the specimens described is
identical with the "central disc ': of the compound
fronds of numerous Monogr apt idee, for no geologist, as
far as I am aware, has described Monograptidcc with com-
pound fronds, unless Dairon's specimens be taken as such.
The early writers on graptolites looked upon the num-
ber of stipes possessed by graptolites as a character of
prime importance in defining genera, such forms as Dicho-
graptus, Tetr agraphia, Didymograptus and Monograptus

366 SCIENCE PROGRESS.

being largely characterised by the possession of eight, four,
two stipes and one stipe respectively. In a recent paper
by Professor Nicholson and the present writer (15) we
have endeavoured to show that this is not the case, but
that the character of the hydrothecae and to a less degree
the amount of angle of divergence of the stipes are of im-
portance. We endeavour to prove that certain grapto-
lites underwent development along parallel lines, passing
through many-branched, eight-branched, four-branched,
two-branched and one-branched forms, thus illustrating the
principle of heterogenetic homoeomorphy advocated by
Mojsisovics, S. S. Buckman and others. If this be allowed,
many of the present genera will have to be abolished and
new ones formed ; but the writers earnestly advocate the
retention of the present genera under existing circum-
stances, and hope that the formation of fresh genera will
be deferred until our views are more fully developed or
perchance disproved, though we do not think that the latter
event is likely.

It will be noticed that the above researches into the
morphology of the graptolites deal mainly with the
celluliferous portions of the polyparies, whilst the study of
the various bodies referred to as concerned in reproduction
has not been largely pursued of recent years.

Passing now to the memoirs treating of the graptolites
as indices of age of the rocks which contain them, it may
be remarked at the outset that recent work has fully estab-
lished the correctness of the views advanced by Lapworth
in his papers on the Moffat series and on the geological
distribution of the Rhabdophora. Perner alone has stood
out for the anomalous occurrences described by the eminent
Barrande in the Bohemian basin, but he does not yet
appear to have studied completely the zonal distribution of
these organisms in that region, though he has added largely
to the number of species occurring in the Lower Palaezoic
rocks of Bohemia. The new species described here and
elsewhere of recent years it is not contemplated to notice in
this article, though they will doubtless give us much
information in addition to that we have already obtained

THE GRAPTOLITES. 367

concerning the morphology and phylogeny of the graptoli-
toidea. It would serve no useful purpose to give details of
the numerous papers which confirm the value of the grap-
tolites for purposes of correlation of the strata. In Britain,
Lapworth himself has described a number of graptolitic
bands interstratified with deposits containing the remains of
other organisms in Ayrshire (16). Much remains to be
done in this respect, for in order to utilise to the utmost the
value of these organisms as stratigraphical indices, it will be
necessary to have a complete correlation of graptolitiferous
strata of all ages, with those which contain these organisms
rarely or not at all. For this purpose all graptolites should
be carefully collected and preserved from out of those
deposits in which they are not frequent, and are associated
with other organisms. They should be looked for especi-
ally in calcareous deposits, for as we have already seen, such
specimens are particularly valuable as furnishing information
concerning the morphology of these fossils. The southern
uplands of Scotland have recently been re-examined by the
geological surveyors, and it is scarcely necessary to state
that they have fully confirmed Professor Lapworth's classifi-
cation of the Lower Palaeozoic Rocks of this region. In
England Professor Nicholson and the present writer have
defined graptolitic zones in the Skiddaw Slates, Llandovery,
Tarannon, Wenlock and Lower Ludlow Beds (17). Messrs.
Lake and Groom have detected the Monograptus gregarius
zone of the Birkhill shales and zones of Monograptus per-
sonalis, M. Flemingii, M. colonius and M. leint wardinensis
near Corwen and Llangollen (18), whilst in a paper which
has hitherto only appeared in abstract, Miss Wood and
Miss Elles have detected several zones of the Birkhill-Gala
beds near Conway. On the Welsh borderland W. W.
Watts has found one graptolitic zone of Wenlock and two
of Lower Ludlow age on the Long Mountain (19). In
addition to this, various other graptolitic zones have been
detected in different parts of Great Britain, and the zones of
the Moffat area have been traced into Ireland. On the
European continent, Linnarsson, Brogger, Tornquist,

Tullberg and others have detected numerous graptolite

26

368 SCIENCE PROGRESS.

zones in Scandinavia, a full account of which appears in
Tullberg's paper on the graptolites of Scania (20), one of
the most valuable of recent contributions to the literature of
the graptolites. Tornquist, Perner, Barrois and others
have also identified various graptolitic zones in Thuringia,
Bohemia and France. In North America the principal
contribution is by our own countryman, Lapworth, who has
identified a number of graptolite zones in Canada, which
are identical with those detected in Europe (21). In
Australia T. S. Hall is studying the well-known Areing
graptolite fauna, and finds that the graptolites here also are
limited to special zones (22). A number of other papers
might be quoted to show the general recognition of the
utility of graptolites for purposes of correlation of strata,
but enough has been said to indicate the manner in which
the work is progressing, and the vast amount which yet
remains to be done in this connection. I cannot leave this
part of the subject without uttering a warning note. More
harm is done by a wrong determination than good by a
correct one. The graptolites are by no means easy of
identification by those who have not made them a special
study, and it is particularly desirable that no determination
should be recorded by tyros, unless it is absolutely certain,
for when once a wrong name has crept into a list it is
exceedingly difficult to remove it. I could give several
instances of very serious mistakes of this kind which have
been made, each of which will have to be corrected else-
where, but it would be invidious to give names in a
general article of this character.

We may now pass on to consider the physical conditions
under which the graptolite-bearing strata were deposited.
There is very little doubt that they were formed in water of
very different degrees of depth, for graptolites are found in
arenaceous, argillaceous and calcareous strata. Thev have
mainly been collected from deposits which there is every
reason to suppose were formed in deep seas, because a much
greater number of individuals occur in a given space under
such conditions than when the deposits were formed rapidly.
The writer has elsewhere given cases of graptolitic deposits

THE GRAPTOLITES. 369

a few feet in thickness, being represented by thousands of
feet in adjoining regions, and one naturally discovers
forms more easily in a few feet of strata than in several
thousand feet where the process of search rather closely
approximates to that for the proverbial needle in the hay-
stack. The evidence which is being gathered shows more
strongly than ever that the thin graptolite-bearing shales,
which for the above reasons have come to be looked upon
as the deposits for graptolites /di?'- excellence, were deposited
slowly in waters some distance from continents, and pro-
bably of considerable depth. The evidence for depth
depends mainly on the nature of the associated organisms,
which are frequently dwarfed, and either blind or with
enormously developed eyes, whilst that for deposition at
a distance from land is confirmed by the ever-increasing
number of cases of association of graptolitic deposits with
others which are composed almost exclusively of tests of
radiolaria. The most striking" case of this has recently
been detected by the geological surveyors amongst the
rocks of the Southern uplands of Scotland (23). Messrs.
Peach and Home have there discovered beds with Tetra-
graptus of Middle Areing Age, separated from beds with
characteristic Glenkiln (Upper Llandeilo) graptolites by a
thin deposit of radiolarian chert. " We thus perceive that
the great mass of strata which elsewhere forms the Upper
Areing, and the Lower and Middle Llandeilo formations
are here reduced to not more than sixty or seventy feet.
Judged by the palaeontological evidence these thin cherts
appear to be a chronological equivalent of thousands of feet
of ordinary sediment in North Wales. They, no doubt,
were deposited with extreme slowness in a sea of some
depth, and over a part of the sea-floor which lay practically
outside the area of the transport and deposit of the terres-
trial sediment of the time."

The graptolites are generally viewed as type-fossils of
the Lower Palaeozoic rocks, and this view is practically
correct. The earliest graptolite which has hitherto been
described, Dichograptus ? tenellns Linnrs., occurs in the
Lingula Flags of Sweden, below the shales with Dictyo-

370 SCIENCE PROGRESS.

graptus flabelliformis Eichw. which are so widely distributed.
This Dictyograptus, by the way. which has a very limited
vertical distribution, is probably in no way related to the
long-ranged Dictyonema. Graptolites are extremely rare
in the Upper Ludlow rocks, and have been detected in the
Lower Devonian rocks of Bohemia, though it is doubtful
whether their asserted occurrences in rocks of Devonian
age in Scotland and the Harz Mountains are correct. It
may be taken as fairly certain that they finally died out in
Devonian times. Between the earliest and latest graptolitic
deposits we have already a large number of graptolitic zones,
which it will be of use to print in one connected list as this
has not been heretofore done. So far as they have been
made out they are, in ascending order, as follows : Lingula
Flags ; (i.) Zone of Dichograptus? tenellus, Zone of Dictyo-
graptus flabelliformis. Tremadoc Slates; Zones of Bryo-
graptus. Areing Beds ; Zones of (i.) Dichograptus, (ii.)
Tetragraptus, (iii.) Didymograpttts indentus var nanus.
Llandeilo Beds; (i.) Zone of Didymograpttts Murchisoni,
(ii.) Zone of Ccenograpttis gracilis. Bala Beds; Zones of
(i.) Climacograptus Wilsoni, (ii.) Dicranograptus Clingani,
(iii.) Pleurograptus linearis, (iv.) Dicellograptus complana-
tus, (v.) Dicellograptus anceps. Llandovery Beds ; Zones of
(i.) Diplograptus acuminatus, (ii.) Diplograptus vesiculosus,
(iii.) Monograptus argenteus, (iv.) Monograptus convolutus,
(v.) Cephalograptus cometa, (vi.) Monograptus spinigerus,
(vii.) Rastrites maximus. Tarannon Beds ; Zones of (i.)
Monographts turriculatus, (ii.) Monograptus exiguus, (iii.)
Cyrtograptus Graycz. Wenlock Beds; Zones of various
species of Cyrtograptus not yet fully worked out. Lower
Ludlow Beds; Zones of (i.) Monograptus bohemicus, (ii.)
Monograptus Alilssoni, (iii.) Monograptus leintzvardinensis.
Upper Ludlozv and Lower Devonian ; Zones of undescribed
graptolites.

It is quite certain that this number will be very largely
increased as a result of further work, but it is sufficient to
show the importance of the Lower Palaeozoic rocks when it
is remembered that many of these Zones contain a fauna
largely distinct from the faunas of the adjoining ones.

THE GRAPTOLITES. 371

When the Zones are worked out more fully than is the
case at present, we shall have a far better gauge of " Geo-
logical Time " than that founded upon the crude estimates
made by measuring thicknesses of strata.

Lastly, the study of graptolites may possibly throw
some light upon climatic change. I have already en-
larged upon this elsewhere (24), and pointed out that the
separation of graptolitic deposits from non-graptolitic ones
amongst the Stockdale shales of the Lake District, the
deposits themselves being lithologically similar, is most
readily explicable by climatic change. The argument
would be stronger had microscopic examination and
chemical analyses of the strata been made, and I should
be glad to supply any one who cares to look into this
question, which is one of some interest, with material for
such examinations.

In conclusion, the above notes will be sufficient to
show the importance which the graptolitoidea have
assumed not only to the geologist but also to the biologist.
That they differ in any remarkable respect, as regards
their teachings, from any other group of fossils is doubtful.
Their special utility lies in the fact that owing to their
characters they are preserved in sufficient numbers to
allow collectors to obtain a large suite of specimens of
almost every species with little difficulty ; the result is that
further advance has been made in their study than in that
of many other groups which like them are only preserved
in the fossil state. One word to the biologists. We are
often told that fossils are of little use on account of the
absence of soft parts, though biologists have not been
much hampered by this when dealing with the Vertebrata.
But to compensate for the want of soft parts, we are furnished
with a countless supply of specimens whose order of appear-
ance and disappearance we are able to a large extent to ascer-
tain, and this is what the biologist can never obtain by con-
fining his attention to recent organisms. From them he has
been able to ascertain that evolution occurs; how it occurs
is left for the palaeontologist to describe. That the study
of these organisms as pursued up to the present has not

372 SCIENCE PROGRESS.

been in vain, is conclusively proved by the best of all tests,
namely, that we are able to predict the discovery of forms
which are afterwards detected by the worker in the field,
to whom we commend this group as one specially worthy of
his attention.

BIBLIOGRAPHY.

(i) LAPWORTH, Charles. Notes on the British Graptolites and
their Allies. I. On an improved Classification of the
Rhabdophora. Geol. Mag., vol. x., pp. 500 and 555,

1873.

(2) LAPWORTH, CHARLES. The Moffat Series. Quart. Journ.

Geol. Soc, vol. xxxiv., p. 240, 1878.

(3) LAPWORTH, CHARLES. On the Geological Distribution of

Rhabdophora. Ann. and Mag. Nat. Hist., ser. 5, vol. iii.,
1879.

(4) Herrmann, Otto. Die Graptolithen familie Dichograptidae,

Lapvv. Kristiania, 1885.

(5) RlCHTER, H. Thiiringische Graptolithen. Zcit. d. Deutsch.

Geol. Gesell., vol. v., p. 439, 1853.

(6) SOLLAS, W. J. On the Minute Structure of the Skeleton of

Monograptus priodon. Rep. Brit. Assoc., 1893, P- 7%l>
1894.

(7) TORNQUIST, S. L. Studier ofver Retiolites. Aftr. nr Geol.

Foren. i. Stockholm Forhdndl, Bd. v., 7, p. 292, 1880.

(8) Perner, J. Etudes sur les Graptolites de Bohbne. Prague,

1894.

(9) TORNQUIST, S. L. Observations on the Structure of some

Diprionidae. Sdrtryck of Konl., Fysiogr., Svesk., Handl.
Ny Folgd., 1892-3, Bd. iv. Lund, 1893.

(10) Wiman, Carl. Ueber Diplograptidae Lapw., and Ueber

Monograptus Geinitz. Bull. Geol. Inst., Univ. Upsala, vol.
i., 1893.

(11) Holm, G. Om Didymograptus, Tetragraptus och Phyllo-

graptus. Aftr. ur Geol. Foren. i. Stockholm Forhdndl.,
1895, translated by Miss Wood and Miss Elles in Geol.
Mag., vol. ii., pp. 433 and 481, 4th Dec.

(12) Hall, James. Graptolites of the Quebec Group, 1865.

(13) Dairon, James. Notes on Graptolites. Trans. Geol. Soc,

Glasgow, p. 176, 1882.

(14) Ruedemann, R. Synopsis of the Mode of Growth and

Development of the Graptolitic genus Diplograptus. Amer.
Journ. Sci., vol. xlix., 3rd ser., p. 453, 1895.

THE GRAPTOLITES. 373

(15) NICHOLSON, H. A., and Marr, J. E. Notes on the Phylogeny

of the Graptolites. Geo/. Mag., 4th Decade, vol. ii., p. 529.

(16) Lapworth, C. The Girvan Succession. Quart. Joum. Geo/.

Soc, vol. xxxviii., p. 537.

(17) Marr and NICHOLSON. On the Stockdale Shales. Quart.

Joum. Geo/. Soc., vol. xliv., p. 654. Also Marr. On the
Wenlock and Ludlow Strata of the Lake District, Geo/. Mag.,
3rd Dec, vol. ix., p. 534, and Notes on the Skiddaw Slates,
ibid., 4th Dec, vol. i., p. 122.

(18) Lake and GROOM. On the Llandovery and Associated

Rocks of the Neighbourhood of Corwen. Quart. Joum.
Geo/. Soc., vol. xlix., p. 426. And P. Lake, On the Denbigh-
shire Series of South Denbighshire, ibid., vol. ii., p. 9.

(19) Watts, W. W. The Geology of the Long Mountain on the

Welsh Borders. Rep. Brit. Assoc., 1890, p. 817, 1891.

(20) TULLBERG, S. A. Skanes Graptoliter. Sver. Geo/. Undersokn.,
_ ser. C, Nos. 50 and 55.

(21) Lapworth, C. Preliminary Report on some Graptolites, etc.

Trans. Roy. Soc. Canada, p. 167, 1886.

(22) HALL, T. S. The Geology of Castlemaine, etc. Trans. Roy.

Soc. Victoria, p. 57, 1895?

(23) Geikie, Sir A. Annual Report of the Geo/ogicai Survey, etc.,

for 1895, p. 27, 1896.

(24) MARR, J. E. On Homotaxis. Proc. Cambridge Phi/. Soc,

vol. vi., pt. ii., p. 74.

J. E. Marr.

INSULAR FLORAS.

PART VI. (b).

IN my article (59) on the flora of the African Islands of
the Indian Ocean, I dealt with the subject in consider-
able detail, but beyond the vascular cryptogams I had very
few data concerning the Isle of Bourbon. Since then
Dr. Cordemoy has published a Flora of the island (60),
which is a consolidation of all the materials he has been
able to collect during the leisure of upwards of thirty years'
residence in the island, though unfortunately without a full
collation with the rich earlier collections in the Paris Her-
barium of Commerson, Du Petit-Thouars, and other botanists.
Moreover, he has not worked out the geography of the
plants to the extent he might have done, so that it takes
some time to find and extract the particulars of special
interest to the geographer. Indigenous and naturalised
plants are included in the same enumeration without any
typographical distinctions ; and the summary is limited to
a table showing the number of species of each natural
order, including naturalised species. A rough calculation
of the number of indigenous species of vascular plants,
described or enumerated, gives a total of about 11 00,
whereof 200 are ferns, and 172 are orchids.' This is nearly
250 higher than Baker's estimate (61) of the vascular plants
of Mauritius; but, although the islands are nearly of the same
size, the mountains of Bourbon rise to altitudes of between
9000 and 10,000 feet, or about 6000 feet above those of
Mauritius ; thus giving an additional climatic zone to the
former island. And an analysis of the components of the
flora shows that Bourbon possesses a much larger temperate
element. But it should be known that Cordemoy takes a
narrower view of species than Baker, especially in ferns ;
and some allowance would have to be made for this in com-
paring the totals. Apart from this divergence, the flora of
the two islands is essentially the same, several genera and
many species being common to both and found nowhere

INSULAR FLORAS. 375

else. The predominating natural orders of vascular plants
occupy nearly the same positions numerically in both islands ;
ferns being first and orchids second, and Leguminosae and
Compositae relatively low down ; very different proportions
from those obtaining in the Madagascar Mora, in which
these four orders occupy reversed positions. Thus : Legu-
minosae, Filices, and Compositae, followed by the Orchideae,
which are represented by just half as many species as the
Leguminosae.

The absence of a number of natural orders from Dr.
Cordemoy's Flora that are represented in Mauritius may
be accounted for partly by the fact that he did not work out
the old collections made before the destruction of the virgin
forests which formerly clothed the island. It is probable
that many species have disappeared from both islands from
the same cause. The following orders known to be, or as
having been, represented in Mauritius are not included by
Cordemoy : Xyridaceae, Scitamineae, Podostemaceae, Myo-
porineae, Bignoniaceae, Lentibulariaceae, Gentianaceae,
Rhizophoreae, Connaraceae, Simarubaceae, Ochnaceae, Bur-
seraceae and Nymphaeaceae. The absence of several of the
foregoing orders might be accounted for without calling in the
theory of destruction, but it would lead too far to attempt the
discussion of the matter here. Myoporum mauritianum is
an instance of a plant, and an order that is no longer repre-
sented, if it ever were ; for there may have been an error
in locality. The only specimen at Kew is labelled as coming
from one small patch at the east end of the island of
Rodriguez, which is some 300 miles distant from Mauritius.
Moreover the Seychelles and Rodriguez between them
possess several natural orders which do not reach Bourbon
or Mauritius, though they are represented in Madagascar.
They are Nepenthaceae, Passifloraceae, Turneraceae, Diptero-
carpeae (?), Ternstrcemiaceae and Dilleniaceae ; whereof the
first and the fourth are essentially Asiatic, the second
and third American, and the two last equally Asiatic
and American. The parasitical Rafflesiaceae are perhaps
the only natural order in Bourbon that is not repre-
sented in Mauritius. Cordemoy records Hydnora afncana

376 SCIENCE PROGRESS.

as common at St. Paul in Bourbon. It inhabits Eastern
tropical and South Africa, though it is not known
from Madagascar or any other of the African islands. Six
or seven species of Hydnora have been described ; all in-
habiting Africa from Abyssinia and Angola southward to
Cape Colony. I have previously noted (62) the discovery of
a member of this order (Cytinus Baroni) in Madagascar.
Since writing that I have seen a third Mexican species.

The intimate relationships of the floras of Bourbon and
Mauritius may be gathered from the presence in the two
islands, and restriction to these islands, of the following
monotypic, mostly very distinct, genera: Cossignya and Dora-
toxylon (Sapindacese), Grangeria (Rosaceae), Roussea (Saxi-
fragaceae), Psiloxylon (Lythracese ?), Fernelia (Rubiacese),
Heterochcenia (Catnpanulacese), Bryodes (Scrophularineae),
Monimia (Monimiaceae) Dictyosperma (Palmae). To these
may be added several other genera of the same geographical
area, represented by more than one species ; in five instances
out of six by three species : Fostidia (Myrtaceae), Pyrostria
and A/y 07itma (Rub'iacedz), Faujasia (Composite), Hyophorbe
and Acanthophcehix (Palmae). Twenty-five other character-
istic genera are restricted to the African region, using that
designation in the sense of including therein the islands
under consideration, Madagascar, and continental Africa.
Trochetia (Sterculiaceae) is remarkable among them as
extending to St. Helena, where it is represented by two
distinct species — or rather was, for one is quite extinct in
a wild state. Psiadia (Composite) has the same range.

Allusion has been made (63) to the phenomenal con-
centration of endemic p